In order to assess the feasibility of subcutaneous administration of Triptorelin with 6-week intervals for the suppression of pituitary-gonadal axis and changes of clinical signs in girls with idiopathic central precocious puberty (ICPP), 46 girls with ICPP were treated with GnRHa. Triptorelin (Decapeptyl, 3.75 mg) was administered subcutaneously (SC) at 6-weeks intervals or intramuscularly (IM) at 4-weeks intervals randomly for more than 12 months consecutively. During GnRHa therapy, clinical parameters and laboratory data, including height, weight, pubertal stage, bone age, uterine volume and ovarian size, serum levels of luteinizing hormone (LH), follicle stimulating hormone (FSH) and estradiol (E2), were monitored and analyzed. It was found that both treatment regimes led to regression of precocious puberty and reversal of secondary sexual characteristics. Breast developments regressed. Uterine volume was decreased after treatment, but there was no statistically significant difference. Mean ovarian volume did not change significantly during treatment. The height velocity was decreased significantly from 6.3+/-1.4 cm/year to 5.8+/-1.2 cm/year in group SC and 6.7+/-1.3 cm/year to 5.4+/-1.0 cm/year in group IM, respectively. The rate of bone maturation was reduced significantly during treatment. The ratio of deltaBA/deltaCA was 1.2+/-0.2 or 1.3+/-0.3 at the onset of therapy and decreased significantly after the treatment to 0.7+/-0.2 or 0.9+/-0.1, respectively. The predicted adult height was increased significantly and progressively during therapy. The levels of serum LH, FSH and E2 returned to the prepubertal condition. No significant side effects of therapy were noted. The most common side effect during SC treatment was that a non-irritating, 1 cm in diameter mass was palpated at the site of subcutaneous injection in the abdominal wall of patients, which disappeared after 6-12 weeks. Two girls had minimal withdrawal vaginal bleeding episodes after the first injection. It was concluded that both IM and SC triptorelin administrations were clinically effective. They induce profound suppression of hypothalamic-pituitary-gonadal axis while stabilizing height velocity, slowing bone maturation and increasing predicted adult height. These results suggest that subcutaneous injection of triptorelin in 6-weeks intervals at a dosage of 3.75 mg be a safe and acceptable regimen for ICPP