Hundreds of thousands of revelers brushed aside their hangovers Saturday and flocked to Rio's elegant city center for the second day of carnival revelry.

Bearded men in drag jostled with grandmothers and young children as drummers beat out intricate samba rhythms accompanying the Cordao de Bola Preta — Rio's most traditional carnival band.

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In the midst of the madness, Norwegian tourist Sjur Andre Midthun, 29, of Oslo stood looking on with his elderly parents, who appeared to be in a pleasant state of shock.

"I think it's crazy, Brazilians just don't care, said Midthun. "There's only 200,000 people in Oslo, here you got a million partying on the street, you can't compare this to Norway."

From Salvador and Recife in the north to the southern metropolitan sprawl of Sao Paulo, Brazilians staged elaborate parades led by topless dancing beauties and massive street parties fueled by bands atop tractor-trailer trucks rumbling slowly through city streets.

Rio's big carnival action comes on Sunday and Monday nights, when the city's top 12 samba schools mount 80-minute spectacles at the 88,500-capacity Sambadrome, featuring hundreds of drummers, thousands of dancers and about a dozen over-the-top parade floats.

But until then, street carnival groups — called "blocos" — own Rio's neighborhoods. As 80 drummers decked out in pink and green marched their way through the bohemian neighborhood of Lapa late Friday, a nearly naked women danced the samba behind them, emptying bars as men spilled into the street to shimmy behind her.

The madness in the streets has gotten so severe that some blocos have started keeping the time and location of their parades secret, to thin massive crowds.

"Every year, more and more blocos pop up spontaneously, so many that most of the e-mails I receive these days are complaining about how there are too many," said Rio de Janeiro Mayor Cesar Maia.

For some the craziness is too much, and many well-heeled Rio residents flee before it starts. Even Maia officially opened the carnival on Tuesday, while hardly anyone was partying, so he could jet to France for vacation.

The Sambadrome competition seems like anarchy, but it is actually a hard-fought competition as each group vies to be declared the year's champion.

That distinction brings little more than bragging rights, but because a single flaw in costumes, floats or dancing can doom a group's chance of winning, the parade at times seems tense.

At the bloco parties, anything goes — making them more and more popular because fans can join in.

Cordao de Bola Preta expects some 600,000 people to turn out for their parade Saturday morning, more than the 400,000 who showed up last year.

"In reality, what we do is more like standing than parading, but we are a very democratic band and we always do our best to please the crowd," said Pedro Ernesto Araujo Marinho, Bola Preta's vice president.

Sometimes there are so many revelers, it is hard to hear the music, and Marinho concedes that if crowds continue to grow, they might have to do something to stem the tide.

One of the city's most popular blocos — known as "Suvaco de Cristo," or Christ's Armpit, because members parade in the shadow of Rio's mountaintop statue of Christ the Redeemer — solved the problem by not announcing when they intend to march.

"It was a very serious problem the year before last, when we had 50,000 people in the streets. It made for an interminable parade," said Joao Regazzi Avelleira, the carnival group's president. This year, he expects 10,000 to 15,000 people.

The Carmelitas group also kept the location of their street party secret, but Liz Desantis, 26, of San Diego, California, managed to get to the hillside in time to see old and young men gyrating to samba in their nun getups.

"It's just mayhem, a crazy party, tons of people," she said.