This volume is the supplemental proceedings of the 13th International Conference on Theorem Proving in Higher Order Logics (TPHOLs 2000) held in Portland, Oregon, USA during August 14-18,2000. In keeping with tradition, TPHOLs 2000 offers this venue for the presentation of work in progress, where researchers invite discussion by means of a brief preliminary talk and then discuss their work at a poster session. The supplementary proceedings is published by the Oregon Graduate Institute (OGI) as technical report CSE-00-009. The TPHOLs conference traditionally changes continent each year, to maximize the chances of researchers all over the world to attend.