The uncoupling of pituitary stimulation and response observed in adults during administration of the luteinizing hormone-releasing hormone analogue, D-Trp⁶-Pro⁹-NEt-LHRH (LHRH_a) suggested that this drug might be useful in treating precocious puberty. We treated five girls with idiopathic precocious puberty (ages two to eight) for eight weeks with daily subcutaneous injections of LHRH_a. The patients had Tanner II to IV pubertal development, advanced bone age, an estrogen effect on vaginal smear, measurable basal gonadotropin levels with pulsed nocturnal secretion, and a pubertal gonadotropin response to LHRH. Irregular vaginal bleeding was present in three patients. LHRH_a significantly decreased basal (P<0.025) and LHRH-stimulated (P<0.01) gonadotropin levels as well as serum estradiol (P<0.05). The vaginal maturation-index score, which reflects the estrogen effect, fell by 25 per cent. Eight weeks after stopping treatment, all hormonal values and the vaginal maturation index had returned to pretreatment levels. These favorable short-term results will need further study before the benefits and risks of chronic treatment with LHRH_a can be adequately assessed. (N Engl J Med. 1981; 305:1546–50.)