In regard to prevalence surveys of MS in US communities, this article considers the relative merits of case finding through hospitals, physicians, M service organisations, neurology practices, death certificates, chronic care facilities and media announcements and lay referrals. The current value ***c hospitals and non-neurological practitioners for case finding is questionable, given the changes in clinical practice with respect to MS and the da*** collection problems inherent with surveys of physicians. We suggest giving priority to the following case-finding methods: manually reviewing potien*** records of neurology practices, screening patient rolls of local MS service organisations and surveying chronic care facilities. In some US*** communities, these methods may need to be augmented by also surveying internists, general practitioners and family practitioners. ***Capture-recapture methodology offers a way to evaluate the completeness of case ascertainment.