In a follow-up study of 40 tall girls treated with intramuscular estradiol and progesterone, the final height, bone age maturation, side effects and acceptance of treatment were evaluated. The mean duration of treatment was 18 months. During treatment, mean height increase was 6.5 cm (height velocity 3.7 cm/year), which is nearly 50% reduction of normal growth rate. The mean increase in bone age was 2.7 years (bone age velocity 1.8 years/year), which approximates twice the normal maturation rate. The mean reduction in final height was 5.0 cm as evaluated by the method of Bayley. Pinneau (BP), 2.9 cm by the method of Tanner et al. (TW) and 3.0 cm by the method of Roche et al. (RWT). The reduction was greatest when treatment was started before menarche, according to all three prediction methods. When treatment was started after menarch the calculated height reduction was greatest according to the BP method. There was good agreement between the three prediction methods in girls with a bone age below 12 years before treatment. In girls with a bone age above 12 years the height reduction by the BP method was much greater than when measured by the other methods. Side effects evaluated at follow-up were minimal and first menstruation occurred within 3 months (mean) after cessation of treatment. The number of pregnancies was estimated to be normal for age. All but three accepted the treatment. It is concluded that this type of treatment must be restricted to girls with severe psychological problems due to excessive height prognosis and selection for treatment must be based on an individualized evaluation.