Background: This study was performed in order to detect the frequency of different types of precocious puberty, predisposing factors and to show which group of patients need to treatment. Materials and Methods: In this study, 74 patients who referred to pediatric endocrine clinic of Imam Khomeini Hospital and private office from 1993-2000 were assessed. A complete history was taken and physical examination was done in all patients by pediatrics endocrinologist. Bone age was done in all patients and specific hormonal tests were measured in some of them. Results: Among 74 patients, 50 cases (67.6 percent) were female and 24 cases (32.4 percent) were male. The age of the patients was between 0.8-10 years old with mean 5.37 year. 75 percent of male patients had central (complete) precocious puberty and 25 percent had peripheral (incomplete) precocious puberty. 40 percent of female patients had central precocious puberty, 46 percent had premature telarche, 8 percent had premature pubarche, 2 percent had premature menarche and 4 percent had other kinds of precocious puberty (one case with hypothyroidism and one case with Mccune-Albright syndrome). 10 percent of female patients with central precocious puberty had predisposing factor and 90 percent of them were idiopathic. 38.8 percent of male patients with central precocious puberty had predisposing factor and 61.2 percent of them were idiopathic. 100 percent of male patients with peripheral precocious puberty had congenital Adrenal Hyperplasia. 38 percent of female patients and 100 percent of male patients needed to treatment. Conclusion: According to this study and references, precocious puberty in female usually benign but in male patients it should be evaluated thoroughly because they usually have a serious disorder which needs treatment.