Formal engineering methods are changing the way that software systems are - veloped.Withlanguageandtoolsupport,theyarebeingusedforautomaticcode generation, and for the automatic abstraction and checking of implementations. In the future, they will be used at every stage of development: requirements, speci?cation, design, implementation, testing, and documentation. The ICFEM series of conferences aims to bring together those interested in the application of formal engineering methods to computer systems. Researchers and practitioners, from industry, academia, and government, are encouraged to attend,andtohelpadvancethestateoftheart.Authorsarestronglyencouraged to make their ideas as accessible as possible, and there is a clear emphasis upon work that promises to bring practical, tangible bene?t: reports of case studies should have a conceptual message, theory papers should have a clear link to application, and papers describing tools should have an account of results. ICFEM 2004 was the sixth conference in the series, and the ?rst to be held in North America. Previous conferences were held in Singapore, China, UK, A- tralia, and Japan. The Programme Committee received 110 papers and selected 30forpresentation.The?nalversionsofthosepapersareincludedhere,together with 2-page abstracts for the 5 accepted tutorials, and shorter abstracts for the 4 invited talks.