In an outbreak of hepatitis B virus infection in a south Wales village 31 cases were identified over 16 months. Spread of the infection was by sharing needles and by sexual contact. Twenty seven patients were known to have symptoms, of whom nine had an anicteric illness. Generally the illness was mild with no deaths, and there was only one chronic carrier. Two patients were only transiently positive for hepatitis B surface antigen. The outbreak was controlled by vigorous contact tracing and counselling. Despite an enormous increase in workload for the general practitioner and problems including disposal of contaminated needles, outbreaks of hepatitis B virus infection may adequately be treated in the community.