Depression is one of the commonest conditions seen by general practitioners. Conventional treatments are typically drug based, and usually involve one of the tricylic preparations. The evaluation of new treatments requires an understanding of the costs and benefits of existing alternatives, to provide a comparative framework for general practitioners and others concerned with the treatment and management of depressed patients. This paper presents estimates of the direct costs associated with the treatment of patients in England and Wales. These amount to some £420 million annually. Pharmaceutical costs represent a relatively small proportion of this total. Substantial indirect costs are generated through lost productivity, and these may exceed £3 billion.