The purpose of our study was to determine if women with polycystic ovary syndrome are more likely than other women with infertility to develop gestational diabetes. All women who were successfully treated for infertility in the reproductive endocrinology clinic at the University of Arizona Health Sciences Center from January 1, 1990, to January 1, 1995, were identified. A retrospective cohort study was performed comparing the incidence of gestational diabetes and abnormal diabetic screening tests among subjects with polycystic ovary syndrome (N = 24) and a general infertility control group (N = 44). The incidence of gestational diabetes diagnosed in subjects with a history of polycystic ovary disease was similar to the incidence of gestational diabetes in subjects with infertility not ascribed to polycystic ovary disease (four subjects, 16.7% v. three subjects, 6.7%; relative risk [RR] 2.05, 95% confidence interval [CI] 0.31-13.57). A greater number of subjects with polycystic ovary syndrome had a positive diabetic screening test compared to the control group (13 subjects, 54% v. 10 subjects, 23%; RR 2.44, 95% CI 1.26-4.71). Our study suggests that women with polycystic ovary syndrome are more likely to have a positive diabetic screening test, but no more likely to have gestational diabetes than other women with infertility.