The festivities began at noon with a drum roll, the firing of a rocket above the crowd and a call in both Spanish and the Basque language from town councilor Javier Eskubi: "Long live the party of San Fermin!"

After Thursday's official sanction, it will be nine days of drinking, drinking, and more drinking. Oh, and a daily dash down the cobblestone streets ahead of the lethal horns of 6 1/2-ton bulls.

The first of eight bull runs begin Friday morning, but the party started Thursday with the traditional "chupinazo." A "chupin" is a small rocket.

Revelers wearing white shirts and trousers, held up their red kerchiefs and shouted: "Long Live!" as champagne bottles popped and onlookers dumped buckets of water on the crowd from surrounding balconies.

It's impossible to escape the bash without a thorough drenching of beer, sangria, water and eggs, but nobody seems to mind.

"We've come to get drunk!" the crowd chanted, and they had come to the right place.

For nine days each year, this northern town is converted into a 24-hour party town, its ancient streets packed with young and old partygoers from Spain, Europe, the United States and virtually every other corner of the world.

Many cavort into the early hours, then go straight from the bars to the famous 900-yard route where the bull runs take place every morning at 8 a.m.

"It's awesome!" said Skippy Haisma, a 25-year-old Australian gripping a large bottle of beer and sitting on a box of booze in the center of the plaza several hours before the chupinazo began. He sported a circular tuft of dyed-red hair, and said he planned to run with the bulls as he did last year.

"I usually party on through the night, then go straight out to the runs. That's how the Spaniards do it," said the Melbourne native, admitting of his previous brush with the bulls: "I've never been so scared in my life, but I can't describe the adrenaline. What a feeling!"

The San Fermin festival dates back to the late 16th century, though its roots reach back further, to the era when Spain was first Christianized.

The festival became famous when it was immortalized in Ernest Hemingway's 1926 novel The Sun Also Rises. A bronze bust of the writer stands proudly outside the bullring where the bull runs end, and Hemingway T-shirts and other knickknacks can be purchased on nearly every street corner.

Pamplona's population of about 250,000 is expected to rise to more than 1.5 million this week, but not everyone in the city looks forward to the San Fermin festival.

Many locals choose to leave town, taking advantage of special offers by travel agents to escape the madness of the bull runs. Countless shops choose to close, boarding up windows to protect merchandise from the throngs of partygoers.

Animal rights activists also make an appearance every year to protest the runs, and bullfighting in general. Several hundred activists ran the length of the famous bull run topless or nearly nude on Wednesday to highlight what they see as cruel treatment of animals.

Others who are not so keen on bullfighting, say they still find it hard to stay away from the party.

"I just came to drink," said Sara Alonso, a 20-year-old from the northern Spanish city of Santander. "But I don't like it when they kill the bulls."

While the runs and subsequent bullfights are nearly always fatal for the bulls, they can also be dangerous for the runners.

Since record-keeping began in 1924, 13 people have been killed during the runs. The last was a 22-year-old American, Matthew Peter Tassio, who was gored to death in 1995.

Many more people are injured, though officials say the runs have gotten safer as more people have heeded advice on ways not to get hurt. One official piece of advice — if you fall in front of a bull, don't lift your head or you might get it knocked off.

Don't drink too much is another important piece of advice, but one many are expected to ignore.