We describe a general model for embedding object-oriented constructs into calculi of mobile agents. The model results from extending agents with methods and primitives for message passing. We then study an instance of the model based on Cardelli and Gordon’s Mobile Ambients. We define a type system for the resulting calculus, give a subject reduction theorem, and discuss the rˆole of the type system for static detection of run-time type errors and for more program verification purposes. In CONCUR 2000, Lecture Notes in Computer Science 1877:504-520, Springer, 2000.