Center Moses Malone dominated the inside with 27 points and Clint Richardson had 22 as a reserve as Philadelphia beat Milwaukee in the first game of the Eastern Conference semifinals.
The second game will be Tuesday night.
The loss snapped Milwaukee's 16-game winning streak at home.
Charles Barkley scored 19 for the 76ers as a reserve, while Maurice Cheeks had 18.
Milwaukee was led by Terry Cummings' 17 points and Sidney Moncrief's 16 -- all in the first half.
In the first half, Malone scored 18 points and Richardson 14 to pace the 76ers to a 66-51 lead.
Most of Malone's points came inside, where the 6-foot-10 center outmuscled Milwaukee's three centers -- Alton Lister, Randy Breuer and Paul Mokeski -- who totaled nine points in the first half, 19 in the game.
"I think my all-around talent is better than them," said Malone, who had six rebounds and blocked two shots. "And to overcome their depth, you've just got to work hard."
The 76ers, who held a 66-51 lead at halftime, settled matters with an 11-0 run, keyed by Barkley's eight points, midway through the third period that increased the margin to 81-59. Milwaukee could get no closer than 87-71 with 1:37 left in the third period.
"Sometimes I don't understand why things happen," Bucks Coach Don Nelson said. "The tone was set in the first quarter. We could not defense Malone with just our big men. Once that was established, it was very difficult to play Philadelphia."