We propose to evaluate the effect on adult height of low dose estrogen, growth hormone, and the combination of low dose estrogen and growth hormone. Patients will be entered into the study from ages 5 to 12 and will be assigned randomly to one of the four groups (the 3 above treatment groups or placebo). The randomized assignment will be double-blind throughout the study. Treatment will be maintained to adult height (the first height measurement at which the preceding annual growth rate was < 1.5 cm). Beginning at age 12, the estrogen treatment in all 4 groups will be changed to a standardized regimen of increasing estrogen dose, so that all children in the study will undergo secondary sexual changes at an appropriate age.