Trends in mortality from all neoplasms and major cancer sites in Switzerland among populations aged between 20 and 44 years are presented. In men total cancer mortality was approximately constant around 270/10(6) between 1951 and 1965, but declined appreciably thereafter to 217 per million in 1980-1989. The overall fall was 20%. The pattern of trends was similar for women, although a modest decline was already apparent in the earlier calendar period, and the overall fall was 29% (from 303 to 215/10(6)). These favourable trends reflect therapeutic advancements for Hodgkin's disease, leukaemias, testis and (chiefly non-epithelial) ovarian cancer, better control of cervical cancer, the long-term decline in gastric cancer, but also the downward trends in cancer of the intestines and a few less common sites, such as gallbladder and thyroid neoplasms for reasons that are not yet clear. Appreciable rises were observed for lung and other tobacco-related sites in women, for the oral cavity in men and (in earlier calendar periods) cutaneous melanoma in both sexes. Although restricted to a selected number of sites, these rises are discouraging, since the causes of these neoplasms have long been recognized. Somewhat discouraging also is the absence of decline in male lung cancer. These problems notwithstanding, the overall pattern of trends in cancer mortality in young Swiss adults over the last few decades is still reassuring, particularly in comparison with those observed in other European countries, and in the more general framework of the debate on the perspectives of progress in cancer control. Although restricted to a small proportion of all cancer deaths, in fact, trends in young adults offer useful indications on the likely future trends in the same generations in the near future, since they reflect more recent changes in the pattern of exposure. The size of the changes, however, will probably differ, since the prevalent cancers in middle age are different from those in the young.