In the film "Last Action Hero," houses explode, cars crash and dead bodies turn up in swimming pools and parking garages, on roof tops--even in a tar pit.

This is the stuff that toys are made of. But children seeking to re-create movieland-style mayhem with the "Last Action Hero" toy line are in for a surprise. The eight-inch plastic figures of star Arnold Schwarzenegger come with ropes, axes, hooks and dynamite--but no guns.

The toy, marketed to children considered too young to see Columbia's PG-13 movie, also comes with this message printed on the box: "In real life, guns and violence are a big mistake . . . never play with real guns."

Mattel's somewhat kinder, gentler super-hero signals a change in the way make-believe violence is being marketed to children, a potentially groundbreaking shift that is emerging at some companies this summer.

For years, the industry has resisted pressure to limit violence because shoot-'em-up toys are very successful. However, increased concern about violent entertainment--leading to this week's historic agreement by TV networks to issue viewer warnings--is causing at least a few toy companies to act.

Sega of America has announced plans to rate its video games the way Hollywood rates movies, to help parents make suitable choices for children. Electronic Arts, a leading maker of video and computer games, said this week that it also is considering a ratings system.

The move by manufacturers to curb violence in toys is not widespread, and some prominent companies, like Hasbro--the maker of G.I. Joe--argue there is no need for reforms. (Unlike the television industry, the toy business does not face congressional regulation.)

Several events in the past year have nonetheless created pressure for change:

* Toys R Us in Canada has refused to sell "Night Trap," a Sega game that depicts bloody attacks on young women.

* In Britain, the same game came under attack on the floor of Parliament. Sega says it will work with the government to develop a rating for "Night Trap."

* In Hawaii, state lawmakers narrowly defeated legislation that would have required retailers to post warnings that so-called "war toys"--action figures, video games and even water pistols--"increase anger and violence in children."

"The toy industry doesn't lead, it follows," said Carolyn Shapiro, editor of the trade magazine, Toy & Hobby World. "If things change outside the industry, it responds. . . . This may be the start of a trend."