9 children with precocious puberty were treated over a period of 6 months to 6 3/12 years with Cyproteron acetate or an Ethisterone derivate. LH-RH tests with radioimmunological estimations of LH and FSH were performed before therapy was begun, during and after completion of treatment. In children with untreated precocious puberty the mean basal LH levels were the same as in normal prepubertal children but the increase and the peak values after i.v. LH-RH were found to be considerably greater than in normals. In the treated patients this stimulatable LH release was suppressed; after completion of therapy it was again elevated. The basal FSH levels in untreated children were elevated; however the increase and the peak values were comparable to the collective norm. Results were not altered considerably by therapy, however these parameters were given elevated after completion of therapy. Despite the marked suppression of stimulatable LH by therapy acceleration of bone age is practically not affected. After completion of therapy this drug-induced suppression of gonadotropines is promptly reversible.