This book constitutes the refereed proceedings of the 7th International Symposium on Frontiers of Combining Systems, FroCoS 2007, held in Trento, Italy, September 16-18, 2009. The 20 revised full papers presented were carefully reviewed and selected. The papers are organized in topical sections on combinations of logics, theories, and decision procedures; constraint solving and programming; combination issues in rewriting and programming as well as in logical frameworks and theorem proving systems.