Robert Stack, 84, a flinty film actor who became an icon of law-and-order television programs such as "The Untouchables" and "Unsolved Mysteries," was found dead May 14 at his Los Angeles area home. He had a heart ailment and had been suffering from prostate cancer, his family told the Associated Press.

Mr. Stack was a polo player and a champion skeet-shooter before parlaying his golden-boy image into film fame.

He debuted in "First Love" (1939), bestowing on young singing star Deanna Durbin a much-ballyhooed screen kiss. It was said to be her first onscreen smooch, but Mr. Stack later said it was her second. He also was in the enviable position of giving Elizabeth Taylor her first screen kiss in "A Date With Judy" (1948).

Largely stuck with bland romantic and adventure fare, he occasionally surmounted his early material. He showed dramatic promise as the young and very blond Nazi sympathizer in "The Mortal Storm" (1940), with James Stewart, and comic flair as the Polish flier who woos a married Carole Lombard in "To Be or Not to Be" (1942).

After Navy service in World War II, Mr. Stack, like many other affable leading men, sought to darken his screen personality with more complex characterizations. He lent a welcome brittleness to such high-wrought 1950s dramas as Budd Boetticher's "The Bullfighter and the Lady," William Wellman's "The High and the Mighty," Sam Fuller's "House of Bamboo" and Douglas Sirk's "Written on the Wind."

For the Sirk film, in which he played the wealthy, alcoholic and impotent husband of Lauren Bacall, he received an Academy Award nomination for supporting actor.

In television, he found his greatest renown, first as Prohibition-era crime-fighter Eliot Ness in "The Untouchables," which ran on ABC from 1959 to 1963. He won a best actor Emmy Award for his work in the series.

He played police figures in later series, such as "The Name of the Game," "Most Wanted" and "Strike Force," and he hosted NBC's popular "Unsolved Mysteries," which re-created unusual cases of disappearance.

Along with other rugged 1950s leading men such as Leslie Nielsen and Lloyd Bridges, Mr. Stack began lampooning his screen image in such films as "Airplane!" (1980), in which he played Capt. Rex Kramer, and "Caddyshack II" (1988). An able raconteur who never took his profession too seriously, he said the roles suited him better than the crime dramas.

In person, he was known for sharing perhaps-apocryphal anecdotes that displayed his comic preferences.

He told a story about an episode that occurred during the shooting of "The Bullfighter and the Lady" on location in Mexico. He said he had plenty of time to frequent the bars with John Wayne, the film's producer. When some locals asked him what he did in World War II, he responded that he "taught machine gun." A mistake in translation turned "machine gun" into raw Spanish slang for "prostitutes."

Mr. Stack was born in Los Angeles into one of the oldest show business families in the state. His ancestors were opera singers and impresarios. His parents divorced when he was young, and he spent his childhood in Europe with his mother. He had to learn English afresh when he returned to Los Angeles to continue his schooling.

He studied drama at the University of Southern California, and in 1939, he met producer Joe Pasternak, who wanted to pair the young man with Durbin.

He said he sought advice from Spencer Tracy about whether he should accept the part or continue his acting studies in school. "Spence told me, 'Look, our business is based largely on opportunity. You may never get another shot like this again. Take it and run.' "

He made more than 40 movies, including "Bwana Devil" (1952), which was the first 3-D feature film, "Good Morning Miss Dove" (1955), "Great Day in the Morning" (1956), "The Tarnished Angels"(1958) and "Is Paris Burning?" (1966).

His autobiography, "Straight Shooting," was published in 1980.

Survivors include his wife, Rosemarie Bowe Stack, and two children.

Robert Stack played crime-fighter Eliot Ness in "The Untouchables."