A rapid growth of the uterus myoma results from the cell hypertrophy, which involves essential ultrastructural changes in the cytoplasm and the nucleus, thus suggesting the intensification cell functions. The increase in the cell volume and intensification of secretion is followed by the enlargement of the interface between the nucleus and the cytoplasm resulting in formation of numerous invaginations of the nuclear membrane. The autoradiographical data demonstrate a considerable DNA synthesis in the peripheral zone of the myoma, unlike the situation seen in the centre of the myoma and the unchanged myometrium, where DNA synthesis is not considerable. The cytospectrophotometric analysis confirms the above data showing the highest content of DNA in the peripheral zone of the myoma.