  This volume of EPTCS contains the proceedings of the Fourth Workshop on Proof
Exchange for Theorem Proving (PxTP 2015), held as part of the International
Conference on Automated Deduction (CADE 2015) on August 2-3, 2015 in Berlin.
The PxTP workshop series brings together researchers working on various aspects
of communication, integration, and cooperation between reasoning systems and
formalisms. These proceedings contain seven regular papers, as well as the
abstracts of the invited talks by Georges Gonthier (Microsoft Research) and
Bart Jacobs (University of Leuven).
