Four boys with hypothalamic hamartomas associated with sexual precocity are reported from the Departments of Pediatrics and Neurosurgery, University of Pittsburgh, and the Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, MD. Two patients were treated surgically by resection using current microsurgical techniques and two received medical management. Precocious puberty caused by hamartomas occurs early in life with enlarged penis and muscular build noted in early infancy. Growth is accelerated and bone age is advanced. Deepening of the voice and the appearance of acne are common. Other clinical findings include mental retardation, behavioral disturbances, and seizures of gelastic, absence, and generalized tonic clonic patterns. In the two patients treated surgically, subsequent growth and development were normal and in two who were diagnosed late in childhood and treated medically, the adult height was not particularly compromised. The authors recommend surgical resection if the hamartoma is pedunculated or in cases where the patient is young and would require years of parenteral medical treatment. The nontreatment option exists because there is no evidence that the tumors will grow or subsequently cause other problems. [1]