On September 22, 1996, at 1215 central daylight time, a Beech B23, N66338, sustained substantial damage during a forced landing near Viroqua, Wisconsin, in rough terrain. The pilot said that the engine quit, after which she switched fuel tanks. The engine then ran for a few minutes and quit again. The pilot reported no injuries. The 14 CFR Part 91 personal flight was conducted in visual meteorological conditions. No flight plan was on file. The flight departed Champaign, Illinois, at 0924 with the intended destination of Lacrosse, Wisconsin. The pilot stated that she asked that the fuel tanks be filled to the top prior to her departure from Champaign. She also indicated that during her preflight inspection she checked and found the tanks to be full. Records at Champaign do not indicate any fueling of the accident airplane on the day of the flight. Records there indicate that the airplane flew twice on September 20, 1996, and that after those flights 11 gallons of fuel were added, which according to standard practice at the fueling point would have raised the fuel to a standard load of 35 gallons. The airplane then flew an additional 7/10 of one hour without refueling. The airplane did not fly again until the accident flight. Sources at Champaign indicate that they use 10 gallons per hour for fuel consumption calculations. According to their calculation the airplane should have departed on the accident flight with a total fuel load of 24 gallons. The "Hobbs" meter after the accident indicated a total time for the accident flight of 2.6 hours. Examination of the airplane at the accident site revealed one quart of fuel drained from the airplane. There was no evidence of leakage, siphoning, or fuel stains on the airplane. Five gallons of fuel were added to the right fuel tank and the engine was started and ran within specifications.