Trends in ovarian cancer mortality over the period 1955-1989 were analyzed for 25 European countries (excluding the Soviet Union and a few small countries) on the basis of the official death certification data from the World Health Organization database. The overall variation in age-standardized ovarian cancer mortality at all ages declined appreciably, from over 17-fold during the period 1955-1959 (i.e., between 10.5/100,000 in Denmark and 0.6/100,000 in Spain, world standard) to 3.4-fold (i.e., between 9.9/100,000 in Denmark and 2.9/100,000 in Spain) in the late 1980s. When a comparison was made between the late 1950s and the 1980s, ovarian cancer mortality increased in most European countries, except Denmark, Sweden, and Switzerland, where certified mortality was already elevated in the late 1950s, although also in these countries the peak rate around or over 10/100,000 was reached during the 1960s. However, when the changes over the last decade were considered, ovarian cancer mortality trends were downward in all Nordic countries, Germany, Switzerland, Austria, and Czechoslovakia. Mortality was rising somewhat, though to a smaller extent, in Ireland, Britain, and Southern Europe. Trends were more favorable in middle-aged women (35 to 64 years), and, to an even greater extent, in young women (aged 20 to 44), among whom substantial declines, particularly over the last decade, were observed in most European countries, approaching 50% in Britain and Scandinavia. These trends are discussed in terms of changes in risk factor exposure (i.e., trends in average parity and oral contraceptive use), diagnostic and therapeutic improvements, ovariectomy, and changes in case ascertainment and certification.