This epidemiological study in Chile shows a marked increase in biliary-tract cancer based on mortality data, from an age-adjusted rate (1970 world population) of 5.1 per 100,000 in 1970 to 12.0 per 100,000 in 1988. There is an increased risk of this cancer in all age groups but especially in young adults (15-44 years). The female ratio of 3:1 persists. The increase in biliary-tract cancer in 1970-1985 was particularly important for young women but occurred in all female age groups whereas in men it was mostly in the elderly (65 years and more) and less in the middle-aged (45-64 years); no changes were observed in young men. Regional differences have begun to be appreciated. One of the factors which may account for this impressive and unexpected increase is the remarkable decrease in cholecystectomy rates. Less than 20% of the 154% increase in biliary-tract cancer mortality in the period 1970-1985 could be attributed to population aging. Improvements in diagnostic methods did not appear to be an important contributing factor. Other factors that could affect this increase in the incidence to epidemic levels include: an increase in the prevalence of cholelithiasis, an increase in the number of typhoid carriers and possible environmental carcinogens.