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. This work covers topics such as abstract models and logics, specialised models and calculi, algebraic and coalgebraic semantics, and system specification and verification.

Invited Talks.- Regular and Algebraic Words and Ordinals.- Logical Semantics of Types for Concurrency.- Deriving Bisimulation Congruences with Borrowed Contexts.- Symmetry and Concurrency.- Contributed Papers.- Ready to Preorder: Get Your BCCSP Axiomatization for Free!.- Impossibility Results for the Equational Theory of Timed CCS.- Conceptual Data Modeling with Constraints in Maude.- Datatypes in Memory.- Bisimilarity and Behaviour-Preserving Reconfigurations of Open Petri Nets.- Free Modal Algebras: A Coalgebraic Perspective.- Coalgebraic Epistemic Update Without Change of Model.- The Maude Formal Tool Environment.- Bifinite Chu Spaces.- Structured Co-spans: An Algebra of Interaction Protocols.- Graphical Encoding of a Spatial Logic for the ?-Calculus.- Higher Dimensional Trees, Algebraically.- A Semantic Characterization of Unbounded-Nondeterministic Abstract State Machines.- Parametric (Co)Iteration vs. Primitive Direcursion.- Bisimulation for Neighbourhood Structures.- Algebraic Models of Simultaneous Multithreaded and Multi-core Processors.- Quasitoposes, Quasiadhesive Categories and Artin Glueing.- Applications of Metric Coinduction.- The Goldblatt-Thomason Theorem for Coalgebras.- Specification-Based Testing for CoCasl’s Modal Specifications.- CIRC: A Circular Coinductive Prover.- Observing Distributed Computation. A Dynamic-Epistemic Approach.- Nabla Algebras and Chu Spaces.- An Institutional Version of Gödel’s Completeness Theorem.- Coalgebraic Foundations of Linear Systems.- Bootstrapping Types and Cotypes in HasCASL.