OBJECTIVE The aim of this study was to determine the ovarian volume by transvaginal ultrasonography in a gynecologically healthy population of women using no contraception, using intrauterine contraceptive device, or using oral contraceptive. METHODS The study had a cross-sectional design. The ovaries of 428 women aged 1445 who contacted the family planning clinic in the county of Funen were examined. Most of the statistical analyses were carried out using standard techniques. However polynominal regression analysis was used to model ovarian volumes as a function of the day of cycle. RESULTS No differences between the volumes of the right and the left ovary were found in any of the groups. Significant differences were found between the ovarian volumes of the three groups. The ovarian volumes were found to be largest in women using intrauterine contraceptive device, lesser in women using no contraception and smallest in women using oral contraception. A significant difference was found of the ovarian volumes throughout the menstrual cycle in women who were not using oral contraception. The ovarian volumes did not change throughout the menstrual cycle in women using oral contraception. In women not using oral contraception the largest ovary increased in volume from the start of the cycle to day 19, thereafter the volume declined. No evidence of any change of volume over the menstrual cycle was found in the smallest ovary and, for women using oral contraception, both ovaries. There was no correlation between age, height, weight, parity, and ovarian volume in any of the groups. CONCLUSIONS The ovarian volumes, in gynecologically healthy women using intrauterine contraceptive device, are larger than in women using no contraception. It appears that oral contraception reduces the volumes of both ovaries in all phases of the menstrual cycle to equal levels.