One boy and 13 girls with central precocious puberty were treated for 1 year using Buserelin, a GnRH analogue, given intranasally (0.3 mg, four times a day). After 1, 3 and 12 months of therapy, the gonadotropin responses to GnRH were abolished in all the patients whereas mean basal serum concentrations of luteinizing hormone (LH) remained similar to those of pubertal controls. During Buserelin treatment, genital development in the boy and breast development in the girls showed no further progress or some regression. In the boy, serum testosterone levels returned to prepubertal values. In the girls, serum oestradiol levels were variable and, in four of them, vaginal smears showed the persistence of a slight oestrogenic effect during therapy. Pelvic ultrasonography did not show any significant variation in ovarian and uterine lengths. Among the 14 patients, 3 had some progression of pubic hair development, irrespective of serum dehydroepiandrosterone sulphate (DHEAS) levels. In eight patients previously treated with cyproterone, elevated prolactin levels were observed before and during the first month of Buserelin administration. During treatment, mean height velocity was markedly reduced from 11.6 to 6.1 cm/year and mean bone age velocity (+/- 1SD) was 0.85 +/- 0.38 year/year. After 1 year of treatment, the differences in predicted adult height ranged between -0.74 and + 1.04 SDS (standard deviation score). These differences were inversely related (r = -0.72) to the prognosis of adult height calculated before treatment. We conclude that, in central precocious puberty, intranasal administration of Buserelin 1.2 mg/day, may arrest sexual development and reduce height velocity and bone maturation. Improvement of adult height prognosis may occur, especially when it was markedly impaired before treatment.