Girls who fail to enter puberty because of hypogonadism, whether caused by hypothalamic-pituitary or by ovarian dysfunction, require estrogen replacement to induce or to complete their pubertal progression. Careful planning of timing of estrogen therapy and of appropriate estrogen dose can result in improved quality of life and in taller adult height compared with the girl who is simply given adult replacement doses. A case is presented illustrating benefits of a conservative approach. The recommendation is to start with a low dose of ethinyl estradiol (100 ng/kg/day), to hold the dose at this level, and only to progress slowly while there is concern about ultimate height.