The KeY System: Integrating Object-Oriented Design and Formal Methods Wolfgang Ahrendt Thomas Baar Bernhard Beckert Martin Giese Reiner Hähnle Wolfram Menzel Wojciech Mostowski Peter H. Schmitt This paper gives a brief description of the KeY system, a tool written as part of the ongoing KeY project, which is aimed at bridging the gap between (a) OO software engineering methods and tools and (b) deductive verification. The KeY system consists of a commercial CASE tool enhanced with functionality for formal specification and deductive verification.