The certificated private pilot and a passenger departed a coastal airport on a night cross country flight to So. Lake Tahoe, CA, with a planned time enroute of 3 hours. About 6 hours after the estimated departure time, the pilot contacted a flight service station, reporting that he was lost and was on top of an overcast in instrument meteorological conditions with less than one hour of fuel remaining. Through communications efforts radar contact with Seattle Center was established; the airplane was located about 110 miles west of the U.S. coast line and given radar vectors to return to the coast. About 15 minutes after radar contact, the pilot reported fuel exhaustion, and indicated that no survival equipment was on board the airplane. Radar contact was lost when the airplane was about 70 miles west of the coast line. A search failed to locate the airplane. The pilot and passenger are presumed to have received fatal injuries and that the airplane was destroyed.