This book constitutes the refereed proceedings of the Second International Conference on Algebra and Coalgebra in Computer Science, CALCO 2007, held in Bergen, Norway in August 2007.

The 26 revised full papers presented together with 4 invited papers were carefully reviewed and selected from 57 submissions. Addressing two basic areas of application for algebras and coalgebras - as mathematical objects as well as their application in computer science - the papers cover topics such as abstract models and logics, specialised models and calculi, algebraic and coalgebraic semantics, and system specification and verification.