A case of recurrent maternal virilization associated with bilateral hyperthecosis of the ovary during two pregnancies is described. In the first pregnancy, serum testosterone increased to the level of 12.5 nmol/l and in the second pregnancy to 35 nmol/l and after delivery to 66 nmol/l. 5 months after the second birth the testosterone level was 2.7 nmol/l and virilization had spontaneously regressed. Puerperal stimulation tests with human menopausal or with human chorionic gonadotropin did not increase ovarian androgen production. Female babies were not virilized.