Tommy Rettig, 54, the first boy who tagged after Lassie during the famous collie's 20 years on the CBS television network, was found dead Feb. 15 at his home in Marina del Rey, Calif. A spokesman for the Los Angeles County Coroner's office attributed the death to "natural causes."

Already an established child star in 1954, Mr. Rettig was chosen over 500 other boys to play the 11-year-old Midwestern farm boy Jeff Miller when "Lassie" premiered on CBS that Sept. 12. "With Lassie, I'd gladly work for free!" Mr. Rettig declared when he got the job.

He stayed with the collie for four years, ultimately handing the pet over to Jon Provost as Timmy and a whole new family in 1958. The dog, actually a series of male collies, had three families and three forest rangers during two decades of televised adventures.

Thomas Noel Rettig, who was born in Jackson Heights, N.Y., made his acting debut at age 6 in a touring company of "Annie Get Your Gun" starring Mary Martin. He landed his first screen role at age 9 and made 17 films, starring with Marilyn Monroe and Robert Mitchum in "River of No Return." He also appeared with Richard Widmark in "The Last Wagon," with Jane Wyman in "So Big," and perhaps most memorably as a boy with a vivid imagination in "The 5,000 Fingers of Dr. T."

Then came "Lassie," and after that came a troubled life filled with failure to land adult roles, arrests and convictions for growing marijuana and for importing cocaine, bankruptcy, divorce and a string of jobs including photographer, tool salesman, computer programmer and health club manager.

Mr. Rettig remained a staunch advocate of recreational drug use throughout his adult life and in 1983 championed a proposed California initiative to legalize marijuana. He said he continued to use marijuana in middle age but gave up stronger drugs when he became a vegetarian.