OBJECTIVE: There is some evidence that use of hormonal contraceptives, particularly the more androgenic formulations, can alter a woman’s glucose tolerance. We examined the association between hormonal contraceptive use, categorized by the androgenicity of the progestin component, and risk of gestational diabetes mellitus (GDM) in a nested case-control study. RESEARCH DESIGN AND METHODS: Case (n = 356) and control (n = 368) subjects were selected from a multiethnic cohort of 14,235 women who delivered a singleton live birth between 1 January 1996 and 30 June 1998, who were screened for GDM at 24-28 gestational weeks, and who were members of Kaiser Permanente for at least 5 years before pregnancy. GDM was defined using the National Diabetes Data Group plasma glucose cutoffs. Information concerning hormonal contraceptive use during the 5 years before pregnancy was obtained from medical charts and some pharmacy data. RESULTS: There was a suggestion that compared with no hormonal contraceptive use, use of a low-androgen hormonal contraceptive before pregnancy was associated with a slight reduction in risk of GDM (odds ratio 0.84 [95% CI 0.58-1.22]), whereas use of a high-androgen hormonal contraceptive was associated with a modest increase in GDM risk (1.43 [0.92-2.22]). CONCLUSIONS: The effects of hormonal contraceptive use on GDM risk may vary by the androgenicity of the progestin component.