OBJECTIVE: To describe the incidence and prevalence of primary biliary cirrhosis in an urban population between 1987 and 1994, using stringent inclusion criteria and a well-defined study area and population. DESIGN: Descriptive study based on a case register compiled by a retrospective and prospective case-finding exercise and examination of case notes. SETTING: The city of Newcastle upon Tyne. MAIN INCLUSION CRITERIA: (1) Definite cases: fulfilling all three of the following diagnostic criteria: positive antimitochondrial antibody (AMA) > or = 1:40; cholestatic liver function tests (LFT); diagnostic or compatible liver histology. (2) Probable cases: fulfilling two of these criteria. SUBJECTS: All cases of primary biliary cirrhosis identified by multiple case-finding methods, alive from 1 January 1987 to 31 December 1994, in the defined area. MAIN OUTCOME MEASUREMENTS: Incidence and point prevalence rates by age and sex. RESULTS: In all, 202 potential cases were identified, of whom 160 met at least two inclusion criteria. In definite cases annual incidence varied from 14 to 32 (mean 22) per million whole population (with no clear trend) and point prevalence rose from 180 per million in 1987 to 240 in 1994. Mean age at diagnosis in cases incident during the study period was 63.2 years (S.D. 11.1 years, range 39.8-85.7 years). CONCLUSIONS: Primary biliary cirrhosis is much more common in Newcastle than has previously been reported anywhere in the world, and prevalence appears to be rising.