The effect of growth hormone (GH) therapy, alone, with oxandrolone (OX), or with estrogen (E) was studied in two randomized investigations. GH was administered daily at 0.375 mg/kg/wk and OX at 0.0625 mg/kg/d. In a separate study of GH, subjects were begun on conjugated E (0.3 mg/d for 6 months, then 0.625 mg/d. Final and near-final heights were compared to the projected adult heights (ProjAH) of Turner girls based on Lyon et al. and to the final heights of 25 American untreated historical control subjects. In the first study, subjects treated with GH alone reached a final height of 150.4 ± 5.5 cm, 8.4 ± 4.5 cm taller than their mean ProjAH; subjects treated with GH + OX attained a height of 152.1 ± 5.9 cm, 10.3 ± 4.7 cm taller than their mean ProjAH. Historical controls had a mean adult height of 144.2 ± 6.0 cm, matching their ProjAH of 144.2 ± 6.1 cm. In the second study, near-final height was determined at a mean age of 16.1 years. Subjects on GH + late E (age >14 years) had a mean height of 150.4 cm, compared to 147.0 cm for subjects on GH + early E (age <14 years). We conclude that GH, with and without OX, increases final height, and that early initiation of E compromises adult height. (Funded by Genentech, Inc.)