A formal language ccsl is introduced for describing specii-cations of classes in object-oriented languages. We show how class speci-cations in ccsl can be translated into higher order logic. This allows us to reason about these speciications. In particular, it allows us (1) to describe (various) implementations of a particular class speciication, (2) to develop the logical theory of a speciic class speciication, and (3) to establish reenements between two class speciications. We use the (dependently typed) higher order logic of the proof-assistant pvs, so that we have extensive tool support for reasoning about class speciications. Moreover, we describe our own front-end tool to pvs, which generates from ccsl class speciications appropriate pvs theories and proofs of some elementary results.