Estrogen treatment in high doses is effective in reducing adult stature in constitutionally tall girls. In this study, growth data of 38 normal girls with a predicted final height beyond 178 cm, are reported. They were treated with ethinyloestradiol in a daily dose of 0.200 mg until the epiphyseal plates were practically fused. In addition, medroxyprogesterone acetate at a dose of 10 mg daily was given for 5 to 12 days every month. The reduction of final height occurred with decreased growth velocity and accelerated epiphyseal closure. The major factor affecting the response to treatment was skeletal age. The lower the skeletal age, the greater the difference between the predicted final height and the final height. This gain was directly related to the growth potential at start of therapy. The best time to start treatment might be the pre-menarche period at a bone age of 12 years. Serious side-effects were not reported, but treatment should be employed only when height prediction is excessive.