TV guest roles included The Love Boat, Buffy the Vampire Slayer, Ally Mc Beal and he was the voice of Clifford the Big Red Dog cartoon series.

Ritter, whose father was country music singer and actor Tex Ritter, had four children and was married to Amy Yasbeck.

"All of us at ABC, Touchstone Television and The Walt Disney Co.

He collapsed while on the set of 8 Simple Rules and was taken to a nearby hospital in Burbank, California.

But doctors were unable to save him, and he died from a previously undetected heart problem.

"All of us at ABC, Touchstone Television and The Walt Disney Company are shocked and heartbroken at the terrible news of John's passing.

Our thoughts and prayers are with his wife and children at this very difficult time," said an ABC spokesman.

His TV movie appearances included "Unnatural Causes," Stephen King's "It" and "Chance of a Lifetime." Ritter won popularity among independent film directors in recent years and, besides "Sling Blade," appeared in "Tadpole" in 2002 and the new feature "Manhood." He appears alongside Thornton in Miramax's scheduled November release of "Bad Santa." Ritter was married from 1977 to 1996 to Nancy Morgan, the mother of his three oldest children. In addition to son Jason and daughter Stella, he is survived by two other children, Carly and Tyler.

Read Also: Adrianne Curry Boyfriend, Married, Husband, Net worth, Bio Most people know Yasbeck as a first-rate actress who brings out the best in every character she wears on set.

But so was Jerry Lewis." He received an Emmy, Golden Globe and other awards for his "Three's Company" role and was honored by the Los Angeles Music Center in June with a lifetime achievement award.

Ritter, whose first steady acting job was a role as the minister in "The Waltons," appeared in more than 50 plays nationwide and won critical acclaim for his recent nine-month run in "The Dinner Party." He had a memorable turn in Billy Bob Thornton's 1996 film "Sling Blade." After "Three's Company" ended, Ritter worried about falling into a typecasting trap.

"I would get scripts about 'a young swinging bachelor on the make,' and I said 'No, I've done that,"' he told the AP.

"What I was looking for in my time off was something a little bit different, a little serious, or funny in a different way." Ritter described his time on "Three's Company" as an education in quick-study acting.

Somers said she had reconciled with Ritter at the request of his wife, actress Amy Yasbeck (search). I am unbelievably sad for his family, and I will miss him." "It's just stunning, unbelievable," said Wilcox, his assistant. "I was the class clown, but I was also student body president in high school," he told The Associated Press in a 1992 interview.