There is a widespread impression that the number of patients with the autoimmune liver disease primary biliary cirrhosis (PBC) is increasing, although its incidence and prevalence vary widely. Using thorough case-finding methods and rigorous definitions to assess changes in incidence and prevalence with time and to explore the symptomatology and mortality of the disease in a large group of unselected patients, we performed a descriptive epidemiological study of PBC in a well defined population over a fixed period of time using established diagnostic criteria and with clinical follow-up of all cases. In a population of 2.05 million in northern England 770 definite or probable PBC cases were identified. Prevalence rose from 201.9 per 10(6) in the adult population and 541. 4 per 10(6) women over 40 in 1987 to 334.6 per 10(6) adults and 939. 8 per 10(6) women over 40 in 1994. Incidence was 23 per 10(6) in 1987 and 32.2 per 10(6) in 1994. Three hundred patients died in median follow-up of 6.27 years (141 liver deaths); the standardized mortality ratio was 2.85. At presumed diagnosis, 60.9% had no symptoms of liver disease. By June 1994 62% of prevalent patients had liver symptoms. PBC is apparently increasing. It is still unclear whether this is because of a true increase, case finding, or increased disease awareness. The study draws attention to (1) high mortality from liver disease and non-liver-related causes even in patients initially with no liver symptoms and (2) apparently poor diagnostic awareness of the disease.