A cohort of 559 patients in Sweden who satisfied predetermined criteria for the diagnosis of primary biliary cirrhosis was followed with respect to the incidence of cancer during the period of 1958 to 1988. The mean follow-up time from the time of primary biliary cirrhosis diagnosis was 9.0 +/- 5.4 yr. During the follow-up period, 148 patients died and the primary cause of death was liver insufficiency. An overall excess risk for cancer, standardized incidence ratio 1.6; 95% confidence interval, 1.1 to 2.2, was found in the cohort. In contrast to previous reports, we found no excess risk for breast cancer (standardized incidence ratio, 0.9; 95% confidence interval, 0.3 to 2.1). The number of hepatocellular cancers in the primary biliary cirrhosis cohort did not significantly differ from expected (standardized incidence ratio, 2.91; 95% confidence interval, 0.4 to 10.5).