Modern clinical terminologies are required to provide a large corpus of concepts to cover the complexity of medicine. It is well recognised that sufficient scalability is likely to be achieved only with those schemes that can build post-coordinated constructs compositionally. Clinical Terms Version 3 (Read Codes) uses a system of templates to both express the semantic definition (atoms) of concepts and to allow qualification of core concepts with additional detail. This common mechanism for expressing both intrinsic semantic information and additional information allows both pre- and post-coordinated concepts to be retrieved from different perspectives and to detect equivalence between alternative representations of the same concept. The practical application and experience of such an approach is described in relation to a live clinical database (Diabeta). The merits of such an approach are outlined and its relationship to other documented mechanisms outlined.