Sex hormone replacement therapy (HRT) in the female adolescent has the following goals: 1. to mimic physiologic puberty; 2. to enhance normal growth; 3. to induce and maintain normal menstruation, 4. to support normal bone maturation and calcification; 5. to initiate and maintain normal brain cell growth and brain plasticity; and 6. to preserve the woman's psycho-sexual well-being. A physiologic peak bone mass during puberty and young adulthood is achieved when HRT is started by the age of 12. Estrogen has a biphasic effect on longitudinal growth, stimulatory at low doses and inhibitory at high doses. Therefore HRT in the adolescent girl is initiated with low doses of estrogen which progressively increase during a two-year period. This facilitates normal longitudinal growth and normal growth of the uterus for normal menstruation and future pregnancy with a donor oocyte. Whether HRT will continue past the normal age of menopause is still controversial.