Olé! The Running of the Bulls festival begins

A reveler falls while others run with a Jandilla's ranch fighting bull during the running of the bulls of the San Fermin festival in Pamplona, Spain, on Tuesday.

A reveler is tossed by a cow with dull horns during a celebration held at the bullring after the running of the bulls of the San Fermin festival in Pamplona, Spain, on Tuesday.

Revelers wearing a local traditional outfit march during the San Fermin procession in Pamplona, Spain, on Tuesday.

Revelers gather to watch Jandilla fighting bulls running at the San Fermin festival, in Pamplona, Spain, on Tuesday.

Revelers run with a Jandilla's ranch fighting bull during the running of the bulls of the San Fermin festival in Pamplona, Spain, Tuesday, July 7, 2015. Revelers from around the world have gathered for the festival.

Revelers run with a Jandilla's ranch fighting bull during the running of the bulls of the San Fermin festival in Pamplona, Spain, Tuesday, July 7, 2015.

The 'Toro de Fuego' (flaming bull) chases revelers through the streets during the opening day of the festival.

Revelers gathered on City Hall Square celebrate after the firing of the txupinazo rocket, which marks the official beginning of the Fiestas de San Fermin in Pamplona, Spain, July 6. 2015. The festival, locally known as Sanfermines, is held annually from July 6-14 in commemoration of the city's patron saint.

A band performs during the opening day or 'Chupinazo.' Hundreds of thousands of visitors from all over the world attend the nine-day fiesta. Many of them participate in the highlight event: The running of the bulls - or encierro - where they attempt to outrun the bulls along an approximately half-mile-long route through the narrow streets of the old city.

Revelers hold their red scarves as mark the kickoff at noon sharp of the San Fermin Festival.

Not for the claustrophobic! Revelers squeeze through Pamplona's City Hall Square.

A man gets some air as he's tossed about during the launch of the chupinazo rocket.

A reveler wearing a bull earring enjoys the atmosphere during the opening day of the Running of the Bulls fiesta.

Festival goers soak each other with wine.

Ivy Mix from Brooklyn, N.Y., is given a drink of sangria.

Revelers throw a bucket of water from a balcony onto the crowd.

And below the balcony, the water lands on party goers.

A red-and-white-clad sea of revelers soaked each other with wine in a packed Pamplona square Monday.

Revelers from around the world kick off the festival. Tuesday is the first of eight days of the running of the bulls.

A woman is sprayed with water as she celebrates.

A sea of participants hold red scarves as they celebrate.

A reveler jumps from a fountain onto the crowd below.

A reveler drinks wine during San Fermin Fiestas. Many others wore it, as their formerly white T shirts attest.

People enjoy the atmosphere during the opening day of the Running of the Bulls festival.

Streets too much? Some people choose to witness the celebration from balconies.

Sangria is the drink of choice, taken from a plastic bottle as partying continues.

People-surfing/people-tossing is just part of the atmosphere.