Background. Women with premature ovarian failure (POF) are treated with estrogen-progestin therapy; however, doubts remain regarding the effect of this therapy on the breasts of women with POF. Objective. To evaluate the breast density of women with POF using estrogen-progestin therapy compared with normally menstruating women. Methods. A cross-sectional study was performed in 31 women with POF using conjugated equine estrogens and medroxyprogesterone acetate and a control group of 31 normally menstruating women, paired by age. All underwent mammography, analyzed by digitization and Wolfe's classification, the latter defined as non-dense (N1 and P1) or dense (P2 and Dy). Parity, breastfeeding and body mass index were evaluated, as well as duration of hormone use and ovarian failure in the POF group. Results. Digitization revealed no difference in mean breast density between the groups: 24.1 +/- 14.6% and 21.8 +/- 11.3% for POF and control groups, respectively. The Wolfe classification also failed to detect any significant difference between the groups, dense breasts being detected in 51.6% and 35.5% of cases in the POF and control groups, respectively. Conclusion. Periods of hypoestrogenism followed by hormone therapy resulted in no changes in breast density in women with POF, compared with normally menstruating women of the same age.2414043