Charles Manson, sentenced as a mass killer, was drenched with paint thinner and set on fire today by a fellow inmate who said Mr. Manson threatened him because of the inmate's membership in the Hare Krishna religious sect, the authorities said.

Mr. Manson, serving a life sentence in the slayings of the actress Sharon Tate and eight others in a cult murder, was treated for second- and third-degree burns in the prison infirmary and was in good condition, said Bob Gore, a spokesman for the State Corrections Department.

Mr. Manson, 48 years old, was in the hobby shop of the California Medical Facility, the state's prison for psychiatric prisoners, when he was attacked by an inmate identified as Jan Holmstrom, 36, who is serving a life term for second-degree murder. Mr. Manson suffered burns over 18 percent of his body, concentrated on his face, scalp and hands, Mr. Gore said.

Mr. Gore said Mr. Holmstrom told officers that Mr. Manson had threatened him for Mr. Holmstrom's religious beliefs.