This volume contains the papers presented, and subsequently submitted for publication, at the 5th Logic Programming Conference, held June 23-26, 1986 in Tokyo. Topics covered include Prolog machine architecture, Prolog processors, variations of Prolog language, and applications of Prolog to natural language understanding, and expert systems. Most of the works reported in the volume are related to the Japanese Fifth Generation Computer Project allowing readers to compare results from this project with those from similar projects currently being conducted in other countries.