Corinthians made a less than ideal start to their Campeonato Brasileiro title defence as they were beaten 1-0 at home by Fluminense on Sunday.
Euzebio scored the only goal in the 72nd minute for Flu as Corinthians, who perhaps had half an eye on this week's Copa Libertadores quarter-final against Vasco da Gama, slipped up.
Flu are also in Libertadores action later this week, against Argentinian side Boca Juniors.
Vasco made a winning start to the season as they beat Gremio 2-1. Fellipe Bastos opened the scoring for Vasco in the 23rd minute, but the lead lasted just three minutes before Fernando levelled.
Alecsandro sealed the points for the hosts in the 69th minute. Half-time substitute German Herrera scored a hat-trick as Botafogo twice came from behind to beat Sao Paulo 4-2.
Sao Paulo led through Jadson at the break, but the introduction of Herrera changed things as he levelled five minutes after the restart, then again from the penalty spot in the 68th minute after Luis Fabiano put the visitors ahead a second time.
Botafogo sealed the points with a quickfire double as Vitor Junior netted after 73 minutes and Herrera completed his hat-trick five minutes later. The win put Botafogo nominally top of the table after one round of matches.
The day's other winners were Internacional and Atletico Mineiro. Inter beat Coritiba 2-0 through first-half strikes from Leandro Damiao and Dagoberto, while Damian Escudero netted in the last minute to give Atletico a 1-0 win at Ponte Preta.
The other two games, Bahia v Santos and Cruzeiro v Atletico Goianiense, finished goalless.
Cruzeiro held on after having Anselmo Ramon dismissed in the 76th minute.