A framework for the semantic description of concurrent object-oriented languages based on CCS is outlined. We discuss how the essential object-oriented features, such as encapsulation, object identity, classes, inheritance and concurrency are captured. Then, the proposed framework is used for defining the semantics of significantly different versions of a toy language which supports the above features. The ease with which the different versions of this language are accommodated provides some evidence for the applicability of the framework for a wide range of languages, as well as its usefulness for comparing different language designs and examining the interaction of a rich set of object-oriented features.