An 80th-minute goal by the Dane Michael Schjonberg was enough to secure maximum points for Kaiserslautern, who are back in the top flight after a one-year absence.
Bayern never produced their dominant form of last year. "We simply didn't do enough to win - but we shouldn't think the worst and now must do some careful analysis," Bayern's coach, Giovanni Trapattoni, said.
His Kaiserlautern counterpart, the former Werder Bremen coach Otto Rehhagel, was happier. "A win like this is particularly good. It will give a real boost to our self-confidence," he said.
Wolfsburg, who secured promotion along with Kaiserslautern last season, also won their first game, beating Hansa Rostock 1-0 with a last-minute goal by Roy Prager.
The other newly promoted side, Hertha Berlin, drew 1-1 at home yesterday with the European champions, Borussia Dortmund, watched by an astonishing crowd of 76,243 at the Olympic stadium. Lars Ricken put Dortmund ahead but Ante Covic levelled. In yesterday's other game, Hamburg came back from 2-0 down to draw 2-2 at home to Borussia Monchengladbach.
The French international defender Laurent Blanc, newly signed from Barcelona, scored twice in six minutes on his debut as Marseilles came from behind to beat Le Havre 3-1 at home in the French League.
Paris St-Germain also relied on their new signings, Florian Maurice and Marco Simone, for their first goal in a 2-0 home win over promoted Chateauroux, Maurice converting a neat pass from the Italian. Laurent Fournier hit the second.
Both sides, aspirants to the title held by Monaco, made a better start to the season than the champions, who were beaten 1-0 at Bordeaux on Friday.Reuse content