He was found by his friend Stacy Sacco around 4:30 a.m.
The death was caused by a heart attack.
According to friends, he has not been sick or ill lately, but it had been reported he had a bad cough and was going to go to the doctor today.
He leaves behind his longtime partner of 41 years Joseph Gramm, who is a retired actor.
Welcome Back Kotter aired from 1975-1979 and was the show that catapulted John Travolta to superstar success. Palillo played Horshack, who was a member of the group called The Sweathogs.
He will forever be remembered as a Sweathog and for going "ooh, ooh, ooh, Mr. Kotter" as his catchphrase on the show.-DocFB