There are different opinions on a possible sex bias in diabetes. In Sweden we have access to data since the 1930s, making it an ideal model. We aimed to study gender differences and time trends in the incidence and prevalence of type 1 diabetes in Sweden. We found 31 articles on incidence and 8 on prevalence (6 overlapping). Times series on incidence were found regarding children 0-15 years of age (with the Swedish Childhood Diabetes Registry, SCDR, since 1977), with up to 14,721 children with diabetes and with a high degree of ascertainment. Incidence time series were also found for subjects aged 15-34 (Diabetes Incidence Study in Sweden, DISS, since 1983), with up to 7,369 subjects and with a lower degree of ascertainment compared to SCDR. Regarding age from 40 years and above fewer studies were found, and with a much lower number of subjects with type 1 diabetes. Diabetes incidence in children has had a relative increase of approximately 2% per year since 1938. Incidence rates in children 0-14 years of age show no gender differences, but in subjects aged 15-39 years a male preponderance up to twofold is found. Figures for subjects 40 years or older are more uncertain, but show a fairly equal incidence among men and women. The male preponderance in type 1 diabetes from age 15 up to 40-50 could be due to hormonal influence, with higher peripheral insulin resistance among men in young adults and younger middle age.