The epidermal nevus syndrome is characterized by the association of epidermal nevi with abnormalities of the skin, skeletal system, central nervous system, eyes, and cardiovascular system, as well as with malignant conditions. We describe a 2-year-old girl with an extensive epidermal nevus involving the left side of the body (nevus unius lateris) and associated with a woolly hair nevus on the left parietal area of the scalp and multiple acquired melanocytic nevi. Idiopathic central precocious puberty characterized by premature breast and public hair development and advanced bone age developed at the age of 20 months. A sharp increase in serum gonadotropins after a luteinizing hormone releasing hormone (LHRH) stimulation test confirmed the presence of central precocious puberty. This is the third reported case of precocious puberty associated with the epidermal nevus syndrome.