The evaluation of the child with isosexual precocious puberty involves family history, clinical findings including bone age, specific medical imaging, and hormonal data. Assessments of all these data, as well as follow-up of pubertal development, are required to decide which patients should be proposed for therapy. Central isosexual precocity, a condition much more common in girls than in boys, is currently viewed as a spectrum of disorders from isolated premature thelarche to borderline early puberty. In some countries, there may be a trend toward earlier onset of puberty. Peripheral isosexual precocity has many different causes, some specific to either boys or girls and others involving both sexes. Treatment of central isosexual precocity is usually based on long-acting forms of gonadotrophin-releasing hormone (GnRH) agonists, which may not be indicated in slowly progressive variants or borderline early puberty because they do not affect final height. In peripheral isosexual precocity, it is often possible to treat the underlying cause. In activating mutations of luteinizing hormone (LH) receptors or Gs&agr;-protein, the aim of treatment is to block hormonal synthesis or action. However, the addition of GnRH agonists is required to treat disorders that are evolving toward central isosexual precocity. In isosexual precocity, preservation of height potential is particularly important in precocious puberty started at young ages.