Two cases of sexual precocity in female children are reported. One child with the McCune-Albright syndrome had her onset of menses at 3 years of age. Surgical removal of an ovary containing luteinized follicular cysts and primordial follicles has resulted in arrest of her sexual precocity over a period of almost four years, giving her a more normal childhood than would otherwise have been possible. The other child has findings diagnostic of the constitutional type of precocity, by far the most common type. Vaginal bleeding in her case began at 4 years of age. In view of the favorable effect of finding and removing a cystic ovary in the child with McCune-Albright disease, this child was explored surgically. There were early adolescent changes in the uterus, tubes and ovaries, but no other abnormalities were found.