The authors examined a group of 10 girls with true sexual precocity. The age of the patients was within the range of 11 months and seven and a half years. Height acceleration was on average almost one year, skeletal age acceleration was on average almost one and a half years; when BA was evaluated according to tables of visualization methods of the Motol Clinic and the TW2 and C method, a marked acceleration of BA was observed in the RUS method. To differentiate incomplete puberty-thelarche-in all girls the stimulation test, using Relefact LHRH (Hoechst), was performed, the diagnosis of true puberty was suggested by LH serum levels elevated above 12 IU/l. In incomplete puberty only FSH was elevated. In all patients oestrogenization of the vaginal epithelium, breast development (M2-3) and pubic hair was present, in three patients menarche. For treatment Decapeptyl-Depot (Ferring) was administered, the longest period of treatment was eight months. Therefore the change of HA and BA was not evaluated, but even during this brief period of treatment regression of pubertal sex signs occurred.