The authors report the clinical and laboratory findings of seven girls with the diagnosis of Rett syndrome seen at the clinic from August 1978 to October 1988. The patient's age varied from two to ten years and they were followed up for 5 years (and 9 months in average. The development milestone started to deteriorate between five and twenty-four months. Acquired microcephaly was present in six patients and three cases had hyperventilation. Generalized tonic-clonic seizures were the most frequent type of seizures (6 patients) beginning between one and seven years and effectively controlled with carbamazepine. The EEG's abnormal findings were spike discharges (5 patients) and paroxysmal high--amplitude theta activity (4 patients). The remaining laboratory tests were unremarkable. The pathogenesis of Rett syndrome has not been determined. The clinical evaluation is intended to contribute to the knowledge of that rather uncommon disease.