To estimate the prevalence of primary biliary cirrhosis in family members with this disease and determine if a family history of primary biliary cirrhosis predisposes to the development of this disease, we performed a retrospective review of charts and a prospective mail survey of patients with primary biliary cirrhosis. Prevalence of primary biliary cirrhosis in family members of 405 patients with disease was compared to known prevalence of disease in the general population. Twenty-six patients with primary biliary cirrhosis had at least one family member with primary biliary cirrhosis. The estimated prevalence per 100,000 was 6420 or 6.4%. Exclusion of family members with primary biliary cirrhosis who were patients in our practice, in order to avoid duplication, changed the prevalence to 4282 per 100,000 or 4.3%. Affected family members included mothers, daughters, sisters, brothers, aunts and cousins. Estimates of prevalence of primary biliary cirrhosis are between 0.7 and 7.5 cases per 100,000. Therefore, compared to estimates in the general population, the prevalence of primary biliary cirrhosis in family members of patients with this disease is markedly increased. A family history of primary biliary cirrhosis is therefore a predisposing factor for the development of this disease.