The importance of diagnosis, both in rendering available the knowledge accumulated in the past and in providing a guide to future developments, has long been emphasized in British psychiatry. Thirteen years ago, Mayer Gross, Slater and Roth (5) observed in the first edition of their textbook that diagnosis “has never been only naming and labelling. Ideally it implies judgment of causation, and even if this is impossible for lack of knowledge it always includes a plan of action, i.e. of treatment. …” The authors contrasted this approach with a derogation of the value of diagnosis which they felt had become extant in certain schools of psychiatry, and they deplored this tendency, stating unequivocally “the contemptuous attitude to diagnosis which is so prominent a feature of many contemporary schools runs counter to the entire spirit of medicine”. The pendulum now appears to be swinging back and, whilst several centres have remained preoccupied with socio-cultural and psychodynamic approaches to psychiatric illness, interest in psychiatric diagnosis has redeveloped both in Great Britain and in the United States (Kreitman, 1961; Kreitman et al., 1961; Ward et al., 1962; Sandifer et al., 1964, 1966, 1968). The phenomenon is probably related to a current tendency to exchange ideas across the Atlantic, and to the need for a common diagnostic code emphasized by cross-national epidemiological data, mental hospital population movement statistics, and studies of the efficacy of treatment. Clearly adherence to universally accepted diagnostic criteria is mandatory if meaningful comparisons are to be drawn from these and other psychiatric statistics obtained from different national settings.