This study evaluated pubertal development, growth and pituitary-gonadal suppression in 21 patients with central precocious puberty treated with buserelin intranasally and switched after a mean of 2.1 yr to depot-triptorelin given im for 1 year. Arrest or regression of puberty was observed in 12 patients while progression of puberty during therapy was seen in 9 patients (6 on buserelin, 2 on triptorelin and 1 on both therapies). The increment in serum LH and FSH concentrations after sc injection of short-acting triptorelin was greater on buserelin than on triptorelin therapy, particularly in patients with evidence of progression of puberty. Height velocity during therapy showed a reduction which paralleled the decelerating phase of the normal pubertal growth spurt. The rate of bone maturation during therapy was inversely related to pretreatment bone age. Predicted final height showed marked individual variations which were inversely related to predicted adult height before therapy. These data indicate that differences in the nature and route of administration of Gn-RH agonist therapy for central precocious puberty can be of importance for inhibition of pituitary gonadotropin secretion and development of secondary sex characteristics. Height velocity and bone maturation are age-related and the change in predicted adult height depends on pretreatment level.