This volume contains the proceedings of the third International Workshop on Computer Aided Verification, CAV '91, held in Aalborg, Denmark, July 1-4, 1991. The objective of this series of workshops is to bring together researchers and practitioners interested in the development and use of methods, tools and theories for automatic verification of (finite) state systems. The workshop provides a unique opportunity for comparing the numerous verification methods and associated verification tools, and the extent to which they may be utilized in application design. The emphasis is not only on new research results but also on the application of existing results to real verification problems. The papers in the volume areorganized into sections on equivalence checking, model checking, applications, tools for process algebras, the state explosion problem, symbolic model checking, verification and transformation techniques, higher order logic, partial order approaches, hardware verification, timed specification and verification, and automata.