LeBron James scored 27 points, finishing two assists shy of a triple-double, as the defending champions Heat picked up where they left off in the NBA playoffs a year ago, never trailing on the way to beating the Bucks 110-87 in Game 1 of an Eastern Conference first-round series on Sunday.
Ray Allen scored 20 off the bench, Dwyane Wade scored 16 and Chris Bosh added 15 for the Heat, who opened their title defence by holding Milwaukee to 42 per cent shooting.
Brandon Jennings scored 26 points and Monta Ellis added 22 for the Bucks, who have not won the opening game of a playoff series since May 2001. Game 2 is Tuesday in Miami.
Also in the Eastern Conference, Paul George scored 23 points and recorded his first playoff triple double to lead Indiana past Atlanta 107-90.
San Antonio beat the Los Angeles Lakers 91-79 in Game 1 of their Western Conference first-round series, with Manu Ginobili and Tony Parker scoring 18 points each, and Kevin Durant scored 24 points as the Oklahoma City Thunder routed ex-teammate James Harden and the Houston Rockets 120-91.
Tim Duncan added 17 points and 10 rebounds for the Spurs. Dwight Howard had 20 points and 15 rebounds, Steve Nash scored 16 points and Pau Gasol added 16 points and 16 rebounds for Los Angeles.
Despite the double-doubles from Howard and Gasol, the Lakers failed to take full advantage of their inside presence, much to the consternation of the injured Kobe Bryant, who watched the national broadcast.
"Post. Post. Post,'' Bryant tweeted in reference to the Lakers' offence.
Bryant is out for the remainder of the season with a torn Achilles.
Los Angeles' length caused San Antonio problems early as the Spurs missed their first three shots - all inside the paint - as they altered their shots to avoid Howard and Gasol.
Nash, who returned after missing nine games with a hip/hamstring injury, gave the Lakers their only lead with a jumper on the game's opening possession.
Duncan broke the drought, hitting a pair of jumpers over Gasol that gave San Antonio a 4-2 lead with 9:33 remaining and the Spurs led the rest of the way.
In Indianapolis, George made just 3 of 13 shots but was 17 of 18 from the free-throw line, had 11 rebounds and 12 assists. It's the first time since 2006 that the Pacers have opened a playoff series with a win.
The best-of-seven series resumes Wednesday at Indy.
On Sunday, the Central Division champs played more like the team that was contending for the No. 2 seed rather than the one stumbling to five losses in its previous seven games.
Atlanta was led by Jeff Teague with 21 points and Josh Smith with 15.
The Pacers weren't sure what to expect after four starters - George, Hill, Roy Hibbert and David West - took a six-day break from game action.
All that rest appeared to help the struggling Pacers get back in sync.
They took advantage on the glass with a 48-32 advantage, forced Atlanta to play a half-court game instead of allowing the Hawks to run and were nearly flawless at the free-throw line.
Indiana made their first 24 free throws, a streak that ended when Lance Stephenson missed the second of two shots in the final minute of the third quarter. The Pacers finished 30 of 34 from the line, compared with 7 of 14 for Atlanta.
At Oklahoma City, after letting Houston wipe away an 11-point deficit in the first half, the Thunder regained control with a 14-1 surge just before halftime and kept pouring it on.
Harden, playing against the team that traded him away just before the season started, had 20 points but the league's second-highest scoring offence was held 15 points below its regular-season average while shooting 36 per cent.