The amnesiac assassin Jason Bourne is back, and this time he clobbered Homer Simpson on his way to scoring the biggest film opening ever for the month of August.

The Bourne Ultimatum, the third movie in the espionage action series starring Matt Damon as a one-time CIA hit man searching for his past, grossed $70.2 million its first weekend to rank as North America's top film at the box office, according to studio estimates on Sunday.

That tally, fueling an unusual late-summer rally at the multiplex, far exceeded the debut ticket sales generated by the first two films in the Universal Pictures franchise.

By comparison, The Bourne Identity opened at No. 2 with $27.1 million in June 2002, and the The Bourne Supremacy landed at No. 1 in July 2004 with $52.5 million. Those two films went on to gross nearly $485 million worldwide combined.

The latest Bourne total marks the biggest first weekend ever for a movie in August, surpassing the $67.4 million opening posted by Rush Hour 2 the same weekend in 2001.

Bourne Ultimatum, which like its immediate predecessor was directed by British filmmaker Paul Greengrass, clearly benefited from the rave reviews it earned for its tightly wound, heart-pounding action.

Exit polls showed the movie played to a slightly older crowd than much of the summer's high-profile popcorn fare, with 57 percent of its audience over the age of 30.

HOT SUMMER

This is beyond all of the special-effects films that are in the marketplace. It offered a different kind of entertainment that's very satisfying, said Nicki Rocco, president of domestic distribution for Universal, a unit of General Electric Co.

Bourne's robust debut continued what has been a very healthy summer for Hollywood, with domestic box office receipts since May 1 up nearly 6 percent compared with the same period last year. This weekend's cumulative gross for all films is up about 25 percent year on year.

It's a very crowded and unusually competitive August marketplace, said Paul Dergarabedian, head of box office tracking service Media By Numbers. August has traditionally been a cool-off month for summer. ... What's unusual this summer is that studios have put some of their biggest films at the end of July and early August.

The continuing commercial strength of hold-over films like I Now Pronounce You Chuck and Larry, Hairspray and Harry Potter & the Order of the Phoenix has also heated up the competition, he said. Those films ranked fourth, fifth and sixth, respectively, this weekend.

Last week's domestic box office champion, The Simpsons Movie, a feature-length version of the long-running TV cartoon, slipped to second place in its second weekend with $25.6 million in U.S. and Canadian ticket sales.

Despite its 65 percent drop-off from week to week, The Simpsons, from News Corp.'s 20th Century Fox, has now racked up about $128.6 million domestically and $315.5 million worldwide.

Another new wide release, the canine superhero comedy Underdog, arrived at No. 3 on the box office chart with $12 million in ticket sales for Walt Disney Co.'s Buena Vista Pictures.

Two other movie debuts posted somewhat disappointing results, owing in part to the crowded field.

Paramount Pictures' Hot Rod, featuring Saturday Night Live star Andy Samberg in his big-screen debut as a self-proclaimed stuntman, grossed $5 million its first weekend to land at No. 9.

Bratz: The Movie, a live-action tween comedy based on the popular fashion doll line, opened at No. 10 with $4.3 million for Lionsgate, a unit of Lions Gate Entertainment Corp.