The concept culture-bound syndrome' (CBS) is elusive. In this paper an attempt has been made to tie the concept down more firmly by proposing a strict definition, examining the appropriateness of this definition in determining the CBS status of two new syndromes (anorexia nervosa and brain-fag) and analysing the usefulness or not of the basic CBS concept. A CBS is defined as a collection of signs and symptoms of disease (not including notions of cause as recently proposed in the anthropological literature) which is restricted to a limited number of cultures by reason of certain of their psychosocial features. Anorexia nervosa appears to fit the definition but further empirical evidence is required to assure that the illness is restricted to Western cultures or cultures strongly influenced by them. The question of the CBS status of brain-fag demonstrates the need to clearly differentiate such disease features as symptom clusters, labels for those clusters, and notions of etiology. Failure to keep such features distinct has led to considerable controversy, but if the proposed definition is strictly adhered to, brain-fag does qualify for the CBS designation. As regards the usefulness of the CBS concept, it is proposed that the question hinges upon whether CBS's signal a difference that makes a difference. It is demonstrated that the CBS concept is useful for medical anthropologists or transcultural psychiatrists who are concerned about relationships between symptom patterns and cultural processes. It is also useful to epidemiologists who, for example, may be interested in estimating the prevalence of depression; it is important to know that they must count some cases of CBS's along with cases of depression with a more typically Western symptomatology. The concept may be redundant for psychopharmacologists who find that they successfully treat many different culture bound syndromes with the same drugs.