Popular movies will always need action stars, but some stars are bound to look more plausible and appealing than others. The writers and directors hired to enhance the starring aspirations of Chuck Norris, for example, appear to face an insurmountable obstacle in the stolid presence of Norris himself.

Currently beating back waves of assassins in an expendable police thriller called "An Eye for an Eye," Norris tends to function more like a bulky prop than a dashing leading man. One envisions stagehands toiling for backbreaking hours to coax him into position for each scene, like the slaves tugging massive stone blocks to the pyramid construction sites in "The Ten Commandments." Once in position, Norris seems incapable of presenting anything but a stony countenance to the camera.

While he's plausible enough in combat, administering punches and kicks from the Korean school to fanatic but inevitably overmatched assailants, Norris doesn't know how to impose himself in repose or to interact naturally with other cast members. You can't tell whether he's ill at ease or merely dense, but the effect is certainly dispiriting. Norris isn't much fun to look at. He's even vaguely absurd, perhaps because of that Little Dutch Boy haircut that crowns his thick, long-jawed, mournful mug. It's as if Hans Brinker grew up to be a palooka.

A forbidding object of contemplation, Norris fails to react on about three or four occasions when buddies try to break through his glum preoccupation with a friendly squeeze on the shoulder. The idea of conventional love scenes with this monolith seems excruciating by definition, so perhaps it's just as well that Norris neglects to make eye contact or share tender sentiments with the nominal leading lady, Maggie Cooper, a newcomer unlikely to attract a second glance from the public anyway.

Now well into his 40s, Norris was once a martial arts instructor to the stars, notably Steve McQueen, and first appeared as a heavy in action movies, notably as Bruce Lee's last opponent in "Return of the Dragon." After Lee's sudden death left a void in the action market, Norris was enterprising enough to promote a modest career in hopes of filling it. "An Eye for an Eye," in which he plays a martial arts spin-off from Dirty Harry, an implacable San Francisco cop named Sean Kane who stalks the drug smugglers who murdered his partner and the partner's girlfriend, is No. 5 in the Norris series. Superficially, it represents something of an improvement, but the indications of elevated production values stemming from snazzy San Francisco locations and splashy fight sequences are still canceled out by the perfunctory nature of the script and the cheerless nature of the star.

Although he brings a certain muscular prowess to the screen, Norris is grievously deficient of charm and humor. Our most enjoyable action stars, from Douglas Fairbanks to Errol Flynn to Burt Lancaster to Bruce Lee, have taken a lighthearted, satiric approach to the depiction of heroic personalities and the execution of acrobatic fighting skills. It's not difficult to believe that Norris can handle himself in a fight, but his cloddish demeanor makes it even more difficult to take vicarious pleasure in his prowess.

Norris may have perceived a huge lumpen appetite for a Caucasian martial arts star in the wake of the incomparable Lee, and the box-office returns suggest that he's satisfied some kind of B-movie mass craving. There's no point in overestimating Norris' status. Obviously, he's no competition for top-flight stars who've made action a specialty, too -- Burt Reynolds, Clint Eastwood and now Harrison Ford, for conspicuous example.

Still, his second-string preeminence is a curious achievement. Richard Roundtree, cast as the police official exasperated with Sean Kane's supposed free-lancing and insolence, projects a far more attractive and intelligent screen presence. At one time, he enjoyed a fleeting eminence as the black private eye Shaft, and I suspect the testiness shown by his character in "Eye" is authenticated by justifiable professional frustration. Outside of racial preference, why should Roundtree play second fiddle to a lunk like Norris