Bioptic material taken from the endometrium of 67 women with the regular menstrual cycle and from 20 patients with irregular bleeding was analysed. In the premenstrual phase of women with the normal cycle and pronounced progesterone action the author found apoptic bodies n 75% of cases. The same percentage (76.92%) of the apoptosis of the endometrium was found in women with irregular bleeding and pronounced progesterone action. The positive finding of apoptotic bodies indicates the beginning of a bionecrotic process tending to generate the endometrium.