  This volume of EPTCS contains the proceedings of the Sixth Workshop on Proof
Exchange for Theorem Proving (PxTP 2019), held on 26 August 2019 as part of the
CADE-27 conference in Natal, Brazil. The PxTP workshop series brings together
researchers working on various aspects of communication, integration, and
cooperation between reasoning systems and formalisms, with a special focus on
proofs. The progress in computer-aided reasoning, both automated and
interactive, during the past decades, made it possible to build deduction tools
that are increasingly more applicable to a wider range of problems and are able
to tackle larger problems progressively faster. In recent years, cooperation
between such tools in larger systems has demonstrated the potential to reduce
the amount of manual intervention. Cooperation between reasoning systems relies
on availability of theoretical formalisms and practical tools to exchange
problems, proofs, and models. The PxTP workshop series strives to encourage
such cooperation by inviting contributions on all aspects of cooperation
between reasoning tools, whether automatic or interactive.
