There is current debate whether prevalence of insulin-dependent diabetes mellitus is increasing in western countries. In Switzerland every male at age 19 years is legally obligated to appear before the Military Conscript Board, where health status is determined by physicians. We analyzed prevalence data concerning the diagnosis of diabetes mellitus in four full surveys (1972, 1982, 1987, 1993). The study included data from 162,607 Swiss males at age 19 years. Case numbers of birth cohorts and prevalence rates per 1000 are the following: [table: see text] Although the number of years surveyed is limited, trend analysis showed no evidence of an increase in the diabetes rates (total chi 2 = 4.953, DF = 3, 0.1 < p 0.2; chi 2 due to linear regression = 3.013, DF = 1, 0.05 < p < 0.1; chi 2 due to departure from linear regression = 1.940, DF = 2, 0.3 < p < 0.5). Overall cumulative incidence of diabetes mellitus was 1.30/1000 conscripts (95% confidence interval: 1.13-1.48/1000). We conclude that, in contrast to reports from other European countries, the cumulative incidence of insulin dependent diabetes mellitus has not increased among cohorts of Swiss males at age 19 years.