The question every first-timer asks is which day to run with the bulls. Behind it sits a belief that somewhere in the eight mornings of the fiesta there is a calmer, gentler or lower-risk day, and that the trick is to skip the first run, avoid the weekend, or wait until the crowds thin out.
The belief matters because it changes how people decide. A runner who thinks a quiet morning is a lower-risk morning may take the decision to run more lightly, and may build a whole trip around a day that, on the evidence we have, changes how crowded the street is far more than it changes how dangerous it is. This article looks at what the calendar really changes, what the public record and one peer-reviewed study can and cannot tell us, and where a runner’s own position on the street comes in.
Encierro founder Dennis Clancey has run the encierro every encierro year since 2007. What follows is mostly his answers, in his own words, with the public record set between them.
Does the Day of the Week Change How Crowded the Route Is?
Yes, and the calendar does most of the work. San Fermín runs from 6 to 14 July, with one run each morning from 7 to 14 July. Which weekday the 6th falls on decides how many weekend mornings are among those eight runs, and the city’s own figures show the route filling at the weekend. Its balance of the 2023 fiesta reported 16,730 runners over the eight runs, 28 percent more than in 2022, with the rise concentrated around the weekend of 7 to 10 July (Ayuntamiento de Pamplona, 15 July 2023). Its 2019 street survey put the average at 1,725 runners a day over the eight runs (Ayuntamiento de Pamplona, 18 July 2019).
For 2027 the pattern is already set by the calendar. If the usual dates hold (the city has not yet published the 2027 programme), the fiesta starts on a Tuesday and the eight runs fall like this:
| Date in 2027 | Day | What happens |
|---|---|---|
| 6 July | Tuesday | Chupinazo, the start of the fiesta |
| 7 July | Wednesday | First encierro |
| 10 and 11 July | Saturday and Sunday | The only weekend runs |
| 14 July | Wednesday | Last encierro, and Bastille Day |
Dennis has watched the effect of where the weekends fall change from one fiesta to the next:
“The changes year to year based on where the weekends fall are quite pronounced. On fiestas where we hit two separate weekends, we have more days where the route will be crowded. Bastille Day certainly influences number increases of French runners late in Fiesta.”
Dennis Clancey, Founder of Encierro
He is careful about how much weight to put on his own impression:
“This is a trend I’ve seen over many years, and some years it’s more pronounced than others. In the end, it’s always a feeling. I can say by trend, since I started running in 2007, the number of people on the run route has increased over that time generally.”
Dennis Clancey, Founder of Encierro
Is the First Morning the One to Avoid?
A piece of advice that travels among English-speaking runners is to skip the opening run on the theory that it will be the most crowded and the most full of beginners. The city’s surveys show that beginners are a large share of the route across the whole fiesta, not only on day one: between 43 and 65 percent of the runners interviewed each year from 2013 to 2019 were running for the first time, as set out in Encierro Research Report No. 1. Dennis’s own experience runs the other way:
“I’ve heard some foreign runners, particularly Americans, will avoid running the very first day because they think it’ll be the most crowded with people that are inexperienced. But in my own experience, I’ve actually historically had some of my best runs on the first day.”
Dennis Clancey, Founder of Encierro
He offered a possible reason, and was clear that he cannot prove it:
“I have no way of confirming this, but that might be. And the fact that people are fresh and there are eight runs, and on that first run, people are getting a feel for the run again.”
Dennis Clancey, Founder of Encierro
He also pointed to who is on the route, and how often they run:
“For context, though, all the Spanish runners, all the local Navarran, Basque runners that are on that run route typically run throughout the year and have more opportunities. So it’s not that they’ve waited all year for these runs again.”
Dennis Clancey, Founder of Encierro
Crowds Have Delayed the Run Before: Calle Estafeta in 1984, a Saturday in 2007
A crowded start is not new. Navarra.com’s history of the run’s start time (Patxi Cervantes, 6 July 2023) recounts that on 7 July 1984 a human blockage on Calle Estafeta delayed the start by seven minutes. On Saturday 7 July 2007 the run began more than six minutes late and without the route cleared, because the crowd would not leave the streets. In 2008, it adds, a group of runners proposed to the encierro board that the start be delayed by an hour, citing overcrowding. Dennis described the crush on the first morning of 2026 in our article on where to stand at 7:30.
Whether waiting for the second morning changes any of this is a separate question, and his answer comes from what he has seen on the route:
“The fact that some people avoid running the first day and go the second day, I have in practice seen the second day always just as crowded as the first day.”
Dennis Clancey, Founder of Encierro
What Does the Research Say About Crowds and Risk?
Dennis has looked at the available data himself:
“I’ve looked at the data personally, and there have been studies done. One particular study admitted that there was no statistical significance to the trends they saw in terms of injury rates on different days. The data does suggest that the injury rates stay constant as the number of people on the route fluctuates.”
Dennis Clancey, Founder of Encierro
The closest peer-reviewed work we know of is a 2008 study in the journal Risk Analysis by Fermín Mallor and colleagues at the Public University of Navarre (doi 10.1111/j.1539-6924.2008.01098.x). The authors found the historical records too patchy to build a detailed statistical model of a runner’s chance of injury. Instead they asked 55 people with direct knowledge of the run, among them runners, surgeons and other health care staff, journalists, civil defense workers, security staff, organizers and herdsmen, to score the risk of hypothetical runs.
One of the factors in those scenarios was crowding, defined as a weekday run (Monday to Friday) or a weekend run (Saturday or Sunday). In the authors’ regression, crowding had a doubtful influence on the experts’ scores, and they kept it in the model only because its p-value was close to 0.10. Which stretch of the route the run was on had no measurable influence at all. The factors that mattered most were personal: the runner’s present condition (rested and sober or not), experience, awareness of the rules, the route and the danger, and physical fitness.
The study measures experts’ judgment of risk, not recorded injuries on particular days, so it cannot settle the question on its own. The year-by-year injury counts that do exist in the public record are set out in Encierro Research Report No. 1. Nothing we found supports the idea of a day with a proven lower risk.
Should You Watch a Run From a Balcony Before You Run?
A commercial version of the first-day advice has become common in Pamplona, built around selling balcony places. Dennis on how it is pitched:
“You also have tour operator companies in town that want to sell balconies. And for them, it has become quite popular to advise their clients to book a balcony the day before their first run. They can watch the run. The stated purpose is that it’s safer to watch a run before you do it for the first time. That said, while I will never steer one of my own clients away from watching from a balcony, we now have things like YouTube where you can watch countless runs and kind of get a feel for the run before going to Pamplona.”
Dennis Clancey, Founder of Encierro
On whether watching first makes a difference to the run that follows, he draws on the clients he has seen do it:
“I’ve had a lot of clients who watched from a balcony the first day and then ran the second day. The reality is, we’ll never know what would have happened if they had run the first. And there’s no convincing evidence I’ve ever seen that someone who watched from a balcony the first day somehow led to some specific action which kept them safe on the second day. It’s possible, but on that I don’t have a specific answer.”
Dennis Clancey, Founder of Encierro
For anyone who wants to watch in person, our guide to watching the running of the bulls in person covers the options, times and prices.
Where You Run Matters More Than Which Day You Run
If the calendar is not where the risk concentrates, the street itself is where the difference shows up. Dennis’s observation about crowd density across the width of the street comes from years of running it:
“One observation as a runner that I have found: over the years the route is becoming more crowded. That is a trend. We know that. But I’ve also found that at the times that I am running at my fastest down the center of the street, attempting to get on the horns of the bull, the street is somewhat less crowded, because in that space there’s less density of humans. Now you’re moving at a much faster pace, and the people typically in that cone are moving equally as fast, and so you don’t get quite the variance in speed that you get if you’re more to the sides of the route.”
Dennis Clancey, Founder of Encierro
He is explicit about the limit of that observation, and about who it applies to:
“That being said, I would never suggest to a first-time runner to try to run down the center of the street, because that requires a lot of skill and timing that the first time you run, you simply don’t have. The people that are running on the horns, and when I say running on the horns, you’re running directly in front of the bull, not impeding it in any way, but running at pace with it, and maybe a step or two in front of it. For someone that is doing that, that is skill that they have developed over a number of years. It’s worth noting that the route often feels much more crowded the more you are to the sides of the route.”
Dennis Clancey, Founder of Encierro
For how Dennis describes the lanes of the street and what to do if you fall, see what to do if you fall in the running of the bulls. For how experienced runners read the density of the crowd, see reading the crowd on the route, and the route map shows each stretch.
Is There a Lower-Risk Day to Run With the Bulls?
Put together, the picture is consistent. The calendar changes how crowded the route is. The best evidence we can find, an expert-judgment study and Dennis’s own reading of the data and his years on the route, does not show that any morning carries a proven lower risk, and his advice to the people he mentors starts from there:
“The more important talking point that I want my own clients, my own mentees to hear is that regardless of what days you do it, you are accepting an extraordinary risk, and that risk doesn’t go away on certain days.”
Dennis Clancey, Founder of Encierro
Encierro never encourages anyone to get on the route in the morning; it exists to help people make an informed decision, including the decision not to run. For a fuller answer for people who have never run, see is running with the bulls safe for beginners, and for how to prepare, the how to run with bulls page.
How Long Should a First-Timer Stay in Pamplona?
Dennis does not prescribe an arrival day:
“Normally, someone’s arrival in Pamplona is built around their own schedule and their own availability. I wouldn’t necessarily recommend one day over another in terms of when to arrive. The majority of people will arrive in time for the first run. But this isn’t a recommendation, necessarily. Day in, day out, the run is largely the same for someone who’s primarily focused on running with bulls.”
Dennis Clancey, Founder of Encierro
On the other end of the trip he is firmer:
“I think if you’re running with the bulls for the first time, you should take a bit of time in the town afterwards to celebrate. Typically, people will go to one of the bars on Plaza del Castillo. A lot of the foreigners will go to Bar Txoko to get a chocolate milk and cognac. People will go to enjoy breakfast. During that breakfast, since often first-time runners are up for much of the night due to nervousness, it’s quite normal to then start drinking after the run. At breakfast, people enjoy vino rosado, rosé wine, and sidra, Asturian cider, and pacharán, a local anise liqueur.”
Dennis Clancey, Founder of Encierro
The chocolate milk and cognac has its own story in the drink Pamplona’s bull runners order after the run, and our piece on the best time to visit San Fermín covers the wider question of when to come.
Frequently Asked Questions
What is the best day to run with the bulls?
No day has a proven lower risk. The calendar changes how crowded the route is: the city’s figures show the weekend is when it fills, and in 2027 the only weekend runs are Saturday 10 and Sunday 11 July. Dennis Clancey’s view, after running every encierro year since 2007, is that the run is largely the same from one day to the next for someone who is there to run, and that the risk does not go away on certain days. If you decide to run, nothing we found supports picking a day on the belief that one morning is gentler.
Is the first day of the running of the bulls the most dangerous?
Nothing we found shows that it is. Beginners make up a large share of the route across the whole fiesta, not only on opening day. Dennis Clancey says he has historically had some of his best runs on the first morning, and in his experience the second day is just as crowded. The first morning does draw big crowds, and crowds have delayed the start before, but a bigger crowd has not been shown to mean a higher rate of injury.
Is it better to watch the running of the bulls before you run?
Dennis Clancey would never steer a client away from watching from a balcony, but of the clients he has seen watch first and run the second day, he has seen no convincing evidence that watching led to anything that kept them safer. Nobody can know what would have happened had they run the first morning. Watching many runs on video before travelling is another way to get a feel for the run. If you want to watch in person, our guide explains where and how.
How long should you stay in Pamplona after running with the bulls?
Dennis Clancey’s advice is not to leave town right after the run but to take time in the town afterwards to celebrate. Many first-time runners have been up much of the night, so breakfast is the usual next stop, and a lot of foreign runners go to Bar Txoko on Plaza del Castillo for a kaiku y coñac. On when to arrive, his answer is that it is built around your own schedule and that most people arrive in time for the first run. He does not recommend one arrival day over another.
Encierro founder Dennis Clancey has run the encierro every encierro year since 2007. His quotes in this article are his own words from our interviews, trimmed only for filler. Every article on the Encierro blog is authored or reviewed by active bull runners with direct experience in Pamplona.