Electroencephalographic changes have been detected in children with premature pubarche. These findings might be the result from past or current central nervous system dysfunction, or from increased sex steroids. In order to Lest the last assertion we have performed electroencephalographic studies in 10 patients (7F, 3M) with congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency, of whom 4 classic and 6 nonclassic forms of the syndrome. Traditional neurologic examination was performed in 7 patients, the result being considered normal in everyone, while evolutional neurologic examination detected hyperactive disturbance and attention deficit in two patients. In another patient, the clinical findings were compatible with delay of neuropsychomotor development. Quantitative electroencephalography with brain mapping in patients over three years-old (n=9), and conventional EEG in the remaining patient, were considered abnormal for age in 8 patients (80%), the record being characterized ns slow in 7 patients. The high rate of electroencephalographic changes in this sample, as well as in premature pubarche, suggests that these findings might result from high inappropriate for age androgenic levels, and warns about the importance or neurologic examination and follow-up in children with CAH.