Seven girls with precocious puberty, idiopathic in 6 and associated with the McCune Albright syndrome in 1, were treated with 70 mg/M2/die of cyproterone acetate (CPA) for 11 to 36 months. Before and during treatment clinical parameters (weight, height, bone age, height velocity, prediction of adult height and pubertal development) were evaluated and plasma hormone assays in basal conditions (LH, FSH, 17 beta-estradiol, progesterone, testosterone, PRL, ACTH and cortisol) and after stimulation (LH, FSH, cortisol, GH) were carried out to assess the efficacy and eventual side effects of CPA. The regression observed in the clinical signs of puberty was considered satisfactory and the increase observed in the developmental quotient indicated an improved prognosis for adult height. No symptoms of adrenal insufficiency were observed but an adrenal suppressive effect of CPA was evident from the response to insulin hypoglycemia observed in 4 patients.