We used the aromatase inhibitor testolactone (40 mg/kg.day) to treat 12 girls with precocious puberty due to the McCune-Albright syndrome for periods of 0.5-5 yr. In the 7 girls who received testolactone for at least 3 yr, the mean +/- SD serum estradiol level was 618 +/- 268 pmol/L at the start of