We studied in 10 children (3 boys and 7 girls), affected by precocious puberty and treated for a period of more than 6 months with the GnRH-analog Buserelin, the efficacy of the GnRH test versus the study of spontaneous nocturnal secretion of LH, testosterone and 17 beta-estradiol as a means of testing the gonadotropin suppression. All the subjects have shown a total suppression of LH during the GnRH test as well as a nocturnal profile of LH, testosterone and 17 beta-estradiol of a prepubertal pattern. Clinically all the patients were treated successfully. Considering the effectiveness of both investigations, we conclude that the GnRH test combined with clinical observation is a single and valid means of testing the pharmacological treatment for precocious puberty.