\s=b\Clinical and laboratory observations were made in three children with isosexual precocity. None of the patients showed abnormalities in neurological or visual-field examinations although one patient had arrested hydrocephalus and a head circumference greater than the 98th percentile for her age and another patient had a history of seizures. Roentgenograms of the skull were normal in all patients. Cranial computerized tomography (CT) identified a lesion in each patient. We believe that cranial CT should be performed in any patient with isosexual precocity in whom a specific cause is not evident or in whom a cerebral cause is suggested even though the patient may be otherwise normal. Cranial CT is a safe, accurate, and noninvasive technique.(Am J Dis Child 134: [25][26][27] 1980)