Objectives: In the present retrospective study, we aimed to determine the frequency and the types of mammographic changes of breast parenchyma in women receiving hormone replacement therapy (HRT). We also investigated whether there was an association between mammographic changes and some clinical and hormonal characteristics of the women on HRT. Methods: One-hundred and eight women were included into the study. Of the 108 women, 19 were climacteric, four premature menopause, 50 spontaneous menopause and 35 surgical menopause. Prior to the start of HRT, an initial mammography was performed and it was repeated at 6- to 18-month intervals according to the women's status. Estrogen alone was started for 35 surgical menopause women and a combination of estrogen plus progesterone for the remaining 73 women. Results: Group I consisted of 96 women with no parenchymal changes or a decrease in parenchymal density on mammography, whereas group II consisted of 12 women with an increase in parenchymal density (11%) during the mean period of 24 months. Endogenous E2 levels were significantly higher in group II than in group I (52.4 ± 42.3 pg/ml vs: 32.3 ± 29.3 pg/ml, P < 0.05). Climacterium or types of menopause did not affect the mammographical density changes. Neither the type nor the duration of HRT had an effect on mammographic density increase. Conclusions: We concluded that the endogenous E2 level might be an important role in screening the women mammographically. Long-term follow-up studies were concluded to be needed in order to evaluate the effects of HRT on mammographic changes.