Forty-five cases of genetic males were assigned and habilitated as females, 43 because of a congenitally defective penis (micropenis with or without hypospadias), and two because of infantile ablatio penis. One of the latter has an identical twin brother as a control. Now 9 years old, she has differentiated a female gender identity in marked contrast to the male gender identity of her brother. Some of the other patients are now adolescent or adult in age. They demonstrate that the twin can expect to be feminine in erotic expression and sexual life. Maintained on estrogen therapy, she will have normal feminine physique and a sexually attractive appearance. She will be able to establish motherhood by adoption.