Formal methods for development of computer systems have been extensively studied over the years. A range of semantic theories, speci?cation languages, design techniques, and veri?cation methods and tools have been developed and applied to the construction of programs used in critical applications. The ch- lenge now is to scale up formal methods and integrate them into engineering - velopment processes for the correct and e?cient construction and maintenance of computer systems in general. This requires us to improve the state of the art on approaches and techniques for integration of formal methods into industrial engineering practice, including new and emerging practice. The now long-established series of International Conferences on Formal - gineering Methods brings 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 and to help - vance the state of the art. This volume contains the papers presented at ICFEM 2009, the 11th International Conference on Formal Engineering Methods, held during December 9-11, in Rio de Janeiro, Brazil.