This volume contains papers based on talks delivered at the Third Workshop on Quantum Field Theory under the Influence of External Conditions, held at the University of Leipzig in September 1995. Contents: Casimir Effect - QED and QCD in External Fields - Ground State in External Fields - Quantum Fields in Black Hole Background - Topics in (Quantum) Gravity and in Quantum Optics - Appendix: Program of the Workshop - List of Participants
