Background.  To investigate the role of the CYP17 gene promoter polymorphism in the pathobiology of uterine leiomyomas in African and Caucasian women.Methods.  During a 6‐month period, 145 Caucasian and black South African women undergoing hysterectomy were included prospectively. Blood samples were obtained for DNA analysis. Factors modifying the risk for uterine leiomyoma growth such as age, parity, age at last birth, weight, body mass index, menopausal status, cigarette smoking and oral contraceptive use were determined.Results.  The risk for leiomyoma development among black South African homozygous carriers of the CYP17 A2 allele was shown to be significantly increased when compared to women homozygous for the CYP17 A1 allele or to heterozygous women. Logistic regression analysis disclosed age, parity and CYP17 polymorphism to have an impact on the presence of uterine leiomyomas (p‐values are, respectively, 0.0006, 0.0001 and 0.03) in black South African women. However, among Caucasian women, logistic regression analysis showed only intake of oral contraceptives to influence the formation of uterine leiomyomas (p = 0.03).Conclusion.  This exploratory trial suggests that among African women, homozygous carriers of the CYP17 A2 allele expose their myometrium to a stronger estrogenic stimulation contributing to the pathobiology of uterine leiomyomas.