LeBron James scored 34 points and Dwyane Wade added 23 as Miami withstood a stellar performance by Boston's Rajon Rondo to beat the Celtics 115-111 in over-time in game two of the NBA Eastern Conference finals.
With Wednesday's victory, the Heat took a 2-0 lead in the best-of-seven series that will send the winners into the NBA Finals against either San Antonio or Oklahoma City.
Rondo was spectacular for the Celtics, playing all 53 minutes and scoring 44 points with 10 assists and eight rebounds.
"He was absolutely phenomenal," Celtics coach Doc Rivers said. "It's tough to have him play that way and not win the game. He basically did everything right."
Rondo's performance was not enough against a Heat team that also got 22 points from Mario Chalmers as they engineered the biggest playoff comeback in franchise history.
The Heat erased a 15-point second-quarter deficit, surpassing the two 14-point post-season comebacks that included the one that won game six of the 2006 NBA Finals against Dallas.
However, there were plenty of twists and turns on Miami's road back in this one.
The Heat appeared to be on their way when they put together a 12-0 scoring run late in the third quarter, taking an 81-75 lead into the final period.
They led in the fourth by as many as seven before the Celtics roared back to regain the lead.
"A lot of contributions from different guys, particularly from the bench," said Miami coach Erik Spoelstra, whose reserves outscored Boston's bench 25-7.
"Tonight was tough," Spoelstra said. "We focused on grinding that overtime and had to do it the tough way."
Wade scored 21 of his 23 points after halftime. He absorbed a hard foul from Kevin Garnett in overtime, made his shot and then the free-throw for a key three-point play.
The extra period came after NBA Most Valuable Player LeBron James missed two shots in the closing seconds of regulation.
The first was a contested lay-up that he missed, but he got the rebound.
With the score tied at 99-99, James watched the clock tick down then took a long shot at the buzzer that bounced off the rim.
"I had a good look, it just didn't go down," James said.
"What I liked, he made winning plays," Spoelstra said of James, noting his 10 rebounds and seven assists. "That's what it's about. It's not always about the shot."
Miami responded by scoring nine straight points to seize control in overtime and James finished an overall impressive night with 10 rebounds and seven assists.
Paul Pierce scored 21 points, Kevin Garnett added 18 and Ray Allen 13 for the Celtics, who will try to bounce back on Friday when they host game three of the series.
"You don't throw it away. You hold it for 24 hours. And then you move on," Rivers said. "We've been very good about that. It's corny, but they've won two games at home and now we go to a place that we're very comfortable in."