A 68-year-old man was found beaten to death and his 82-year-old sister lying beaten and unconscious yesterday in the woman's Oakton home, Fairfax County police reported.

The dead man was identified as John B. Bell, of 10154 Palmer Dr., Oakton. His sister, Mary Bell, of 2910 Hunter Mill Rd., the scene of the incident, had been severely beaten about the head and body, police said. She was listed in fair condition last night at Fairfax Hospital.

According to neighbors, John Bell had been living almost continuously at the Hunter Mill home recently in order to care for his sister, who was nearly incapacitated.

Police said John Bell's daughter Barbara went to her aunt's two-story frame home about 5 p.m. after being unable to contact her father there. She found his body on the floor of an upstairs bedroom and, moments later, discovered Mary Bell lying unconscious on a bed in another bedroom, they said.

Police said last night they had determined no motive for the slaying and assault, and said they had found no sign of forced entry at the home. It could not be immediately determined whether anything was taken from the home, they said.

A police spokesman said the attacks apparently occurred early yesterday, or possibly late Saturday night. He declined to provide further details. An autopsy is scheduled for today.