On July 23, 1997, at 1115 central daylight time, a Cessna 188B, N4926R, sustained substantial damage when directional control was lost while landing on a private strip, three miles east of Adams, Nebraska. The airplane exited the runway and impacted trees. The pilot reported no injuries. The right brake master cylinder was found to be empty on examination. The 14 CFR Part 137 flight was operating in visual meteorological conditions. No flight plan was on file for the local flight. The flight departed for an aerial application at 0900. The pilot said that on rollout after landing, the right brake did not work and the airplane exited the runway and ran into trees. He said that on previous flights the brakes had operated normally. He said that he had not had to service the brakes and did not know of any leaks which could be attributed to the brake system. A post accident examination of the airplane found the right brake master cylinder empty of hydraulic fluid. The last inspection of the airplane was an annual inspection on June 1, 1997. The airplane had operated 32 hours since the inspection. There was no indication of a preexisting hydraulic fluid leak in the brake system.