['Precocious puberty (PP) in girls with McCune-Albright syndrome (MAS) is characterized by episodic development of large unilateral ovarian cysts followed by sudden onset of vaginal bleeding. Some patients experience frequent bleeding as well as accelerated linear growth and advanced skeletal maturation. The use of anastrozole for the treatment of PP in this condition has not been well studied.', 'The objective of the study was to determine the safety and efficacy of the aromatase inhibitor anastrozole for the treatment of PP in girls with MAS.', 'This was a prospective international multicenter study in which subjects received anastrozole 1 mg daily for 1 yr.', 'Twenty-eight girls 10 years of age or younger with MAS and progressive PP were enrolled.', 'Vaginal bleeding, rate of skeletal maturation (change in bone age over change in chronological age), growth velocity, and uterine/ovarian volumes were measured. These indices were compared with a 6-month pretreatment interval.', 'No difference in vaginal bleeding (mean number of days per year) was noted. Mean change in DeltaBA/DeltaCA, which was 1.25 +/- 0.77 at baseline, was -0.25 +/- 1.02 at study end (P = 0.22). Average growth velocity z score was 1.40 +/- 3.15 at study entry and 0.26 +/- 2.71 at 12 months (P = 0.10). Mean ovarian/uterine volumes were unaffected by anastrozole, and no significant adverse events occurred.'] Is the aromatase inhibitor anastrozole ineffective in the treatment of precocious puberty in girls with McCune-Albright syndrome?