The basic descriptive epidemiologic data on stomach cancer occurrence in Italian regions are presented and discussed. Incidence and prevalence were estimated from official mortality and survival data provided by four population-based Italian cancer registries. Age-adjusted mortality, incidence, and prevalence rates are presented by region for the year 1990. Time trends of incidence and their projection for the year 2000 are also presented by region and three broad age classes. Although the occurrence of stomach cancer has been decreasing in Italy and most western countries over the last decades a substantial slowing down of this decrease was evidenced in Italy, especially for women under 65 and for the regions of southern Italy. A marked tendency towards a reduction of geographic heterogeneity in stomach cancer occurrence was also shown. Such a phenomenon is consistent with the observed changes of dietary habbits in Italian regions. The regions of Umbria and The Marches seem to emerge as new areas at relatively high risk of stomach cancer incidence and mortality. About 45,000 prevalent cases were estimated in Italy by 1990, half of which have been diagnosed before 1984.