By the term _precocious menarche_ we understand the pathological state in which a typical, four-weekly, sanguineous discharge from the female genital organs sets in at an abnormally early age, and is to be regarded as a symptom of a premature sexual development. Very commonly such children with precocious menstruation and premature sexual development, exhibit a comparatively high body-weight, great development of fat, early dentition; they look older than their years; and they have genital organs that also develop very early, with hair on the pubes and in the axillæ; the labia majora and the breasts resemble those of full-grown women, and the pelvis also has the adult form. Commonly also the sexual impulse develops early, whilst, in other respects, the intellectual development lags behind the physical. It is most probably a primary hyperplasia of the ovaries that gives rise to precocious menstruation, the ovarian follicles ripening earlier than usual. Frequently other pathological processes are associated with this early sexual development, such as general lipomatosis, rachitis, and new growths of the ovaries. In several cases of this nature, early conception has also been observed. According to oriental tradition, Khadijah was married at the age of five years to the prophet Mohammed, who cohabited with her three years later. Even if we except those cases in which in earliest infancy there is a sanguineous discharge from the vagina which remains, however, an isolated occurrence, or if repeated is repeated a few times only and at quite unequal intervals (cases in which the bleeding cannot be regarded as menstrual—such, for instance as were reported by _Eröss_ of six new-born female infants in whom a sanguineous discharge from the vagina appeared three or four days after birth and lasted two to five days, the infants not remaining subsequently under observation),—numerous well-authenticated cases yet remain in which menstrual hæmorrhage was observed before the end of the first year of life. One case, even, is recorded by _Bernard_ in which from the time of birth to the twelfth year menstruation with molimina occurred every month, lasting two days; from the twelfth to the fourteenth year menstruation ceased, recurring subsequently at irregular intervals. In the recorded cases of such precocious menstruation the menstruation recurred as a rule at regular intervals of four weeks; only in quite exceptional cases were the intervals three to five months. Some of the most striking and well-authenticated cases of precocious menstruation recorded in the recent literature of the subject are appended.