On April 9, 1993, at 1416 hours Pacific daylight time, a Cessna T310R, N3532G, landed gear up on Runway 27 at the Pine Mountain Lake Airport, Groveland, California. The pilot was completing a visual flight rules personal flight. The airplane, registered to and operated by the pilot, sustained substantial damage. The certificated private pilot and passenger were not injured. Visual meteorological conditions prevailed at the time. The flight originated at the Nut Tree Airport, Vacaville, California, at about 1345 hours. The pilot indicated during a telephone interview that he entered the airport traffic pattern midway on the downwind leg and forgot to extend the landing gear. The pilot did not recall hearing the airplane's gear warning horn. As the airplane propellers struck the ground, the pilot attempted to go around. The airplane veered off the runway before coming to a stop. The pilot stated on his pilot accident report that there were no mechanical failures or malfunctions with the airplane before the accident.