This volume contains the proceedings of the Sixth International Workshop on Automated Verification of Critical Systems (AVoCS 2006), which was held on September 18–19, 2006 in Nancy, France. The workshop is devoted to techniques and tools for the verification of critical systems, and applications thereof. It aims to being together researchers from academia and industry who have an interest in formal verification, interpreted in a broad sense. Previous instances of AVoCS were held in Warwick (2005), London (2004), Southampton (2003), Birmingham (2002) and Oxford (2001).