The demographics of primary biliary cirrhosis in Ontario, Canada, are described. Two hundred and twenty-five primary biliary cirrhosis patients were identified by 85 of 502 gastroenterologists (or internists) practicing in Ontario acute care hospitals that have 150 or more beds. Two hundred and six patients were verified as being antimitochondrial antibody-positive, resulting in an incidence of 3.26 per million per year and a prevalence of 22.39 per million. Questionnaire data were obtained on 88.5% of these patients. Twenty-nine percent of the patients were found to be asymptomatic. Geographical clustering and racial predisposition were not seen. No increase in breast cancer prevalence was noted. By the time the diagnosis of primary biliary cirrhosis was established, the patients had consulted a median number of 3.5 physicians. Fatigue was reported as the most disabling symptom. The diagnosis of primary biliary cirrhosis in patients referred from across the province of Ontario was independently confirmed by us, using standard criteria (antimitochondrial antibody testing and liver biopsy), and was found to be reliable. (HEPATOLOGY 1990; 12:98–105).