This study evaluates the cumulative incidence of Type 1 (insulin-dependent) diabetes mellitus in male army conscripts 0-18 (inclusive) years of age in the Netherlands (birth cohorts) over 10 years. Data from 2136 cases were retrieved from files of the conscript registry of the Royal Dutch Army. Ascertainment was sought by the capture-recapture method, achieving an average ascertainment rate of 89.7%. Poisson regression modelling was used to determine the change in incidence over time. A significant non-linear increase in the incidence of insulin-dependency in the birth cohorts of 1960-1970 was found. The cumulative incidences of the early birth cohorts 1.85/1000 (1960), 1.76/1000 (1961), 1.11/1000 (1962) were considerably lower than of the later birth cohorts 1.96/1000 (1968), 2.11/1000 (1969), 2.12/1000 (1970). Overall the risk of Type 1 diabetes increased on the average 4.4% with each annual birth cohort. Only for the 1962 birth cohort was a significant dip in the incidence observed. The results indicate a rapidly increasing incidence of diabetes in males in the Netherlands consistent with the concurrent rapid rise in Northern Europe, found in both sexes.