The paediatric endocrinologist is frequently asked whether pubertal development in a girl is normal, early or too early (precocious). This review will cover all clinical expression of premature development of puberty: central precocious puberty (neurogenic, secondary, and idiopathic) where treatment with GnRHa is considered, early puberty, partial puberty or pubertal variants and peripheral or pseudo precocious puberty related to an antonomous hypersecretion of estrogens by the ovaries. A special attention should be paid also to the role of environmental disruptors in the development of peripheral precocious puberty. GnRHa treatment should be considered only when evidence of central activation of the gonadotropic axis is proved by the LHRH-test.