The reported incidence and prevalence of primary biliary cirrhosis has risen in the past 10 years in Northern Europe. In order to determine whether this is a genuine increase in the disease or an apparent increase due to increased awareness of physicians and more ready diagnosis, we have carried out a comprehensive epidemiological study of primary biliary cirrhosis. All possible cases from 1965-1987 were examined using the best case finding methods available. In a relatively stable population of about 1.92 million we identified 471 patients with 'possible' primary biliary cirrhosis and 347 with a definite, histologically confirmed, diagnosis. Prevalence rose from 18/1,000,000 in 1976 to 128.5/1,000,000 in 1987 (276/1,000,000 in women greater than 18 years). Increased awareness and availability of interested physicians seemed to be important contributing factors to the rise in prevalence. No important geographical clustering of cases was noted.