On September 20, 1993, approximately 1940 hours eastern daylight time, a Beech BE18-C45G, N80323, piloted by the commercial pilot/airplane owner, sustained substantial damage when the landing gear collapsed during the landing roll at Jeffersonville, Indiana. The pilot, the sole occupant, reported no injuries. Visual meteorological conditions prevailed for the local flight, no flight plan was filed. The flight operated under 14 CFR Part 91, and originated from Jeffersonville, Indiana, approximately 1930 hours. The pilot stated he had performed two takeoffs and landings without incident. When he attempted to extend the landing gear for the third landing, it did not extend. He reported after cycling the landing gear handle several times, he utilized emergency landing gear extension methods to lower the gear. The pilot stated he cranked the gear down until he felt resistance. The landing gear indicator flags did not indicate the gear was down and locked. The pilot requested and received verification from ground personnel that the landing gear appeared to be extended. He stated he used normal approach procedures and airspeeds, and the touchdown and roll out seemed normal. The pilot reported when he "...made a light brake application to finish slowing...the landing gear folded back into the wheel wells." Postaccident inspection revealed the main landing gear slide tubes were lacking lubrication. The right main gear slide tube was corroded. Impact damage precluded a complete evaluation of the electrical system, but the electrical landing gear motor was capable of normal operation. An FAA Inspector statement is appended. The most recent maintenance performed on the airplane was an Annual Inspection completed November 3, 1992. The airplane operated 16.25 hours since that inspection.