Seasonal variations in the morphometry of the ovary and uterus, and in progesterone and 17β-oestradiol production in 37 brown hares (Lepus europaeus), 10 in spring, 7 in summer, 14 in autumn, and 6 in winter, are reported. Evaluation of the relative volume of primary and growing follicles, and stroma in the hare ovary revealed a stable level of primary follicles during the year. The highest relative volume of growing follicles was found in the autumn, with a similar value in winter. As the relative volume of growing follicles increased, the amount of stroma decreased. The lowest relative volume of stroma was found in the autumn (90.1%) and the highest in the spring (97.3%). No significant differences were found in the relative volumes o f follicles and stroma in the ovary. The diameter of primary follicles ranged from 30.8 to 35.9 µm during the year, with no significant seasonal difference. The diameter of growing follicles ranged from 139 to 222 µm. The highest relative volume of endometrium in the uterus occurred in the autumn and summer. This difference was significant in comparison with spring (P<0.05). The height of the endometrium was highest in the summer and lowest in the winter. Detailed analysis of the endometrium showed that the highest relative volume of the surface epithelium was in the spring (6.5%), the highest relative volume of glandular epithelium in the winter (22.4%), and the highest relative volume of stroma in the autumn (85.8%). The highest surface epithelium was found in the spring. The average diameter of uterine glands was highest in the spring (63.5%), but the differences between seasons were not significant. Analysis o f progesterone and 17β-oestradiol in hare blood showed that the highest levels of progesterone occurred in the spring (22.91 ng/ml). Significant differences were found in the progesterone concentration between spring and autumn (P<0.001). For 17β-oestradiol, the highest concentrations occurred in the winter and the lowest in the summer. The results of this study clearly demonstrate that the highest follicular growth in the brown hare occurs in the autumn, which corresponds with the highest relative volume of uterine glandular epithelium in winter as well as with the highest diameter of uterine glands in the spring. We suggest that in our conditions, the reproductive activity in the female brown hare starts in the autumn.