A follow-up study was made on 304 children (164 boys, 140 girls) with convulsive disorders, excluding occasional convulsions, in the first year of life. All patients except 45 who died were followed until 6 years of age or older. At the final follow-up, the subjects were divided into six groups according to the degree of mental and physical development (groups I-VI). Seizures were regarded as absent if the patient had been seizure free for more than 3 years. At the final follow-up, seizures had ceased in 57.7%, and 43.4% had normal mental and physical development (group I). As to the initial diagnosis, the percentage of group I at the final follow-up was 81.8% with febrile convulsions and 37.6% with epilepsy. In patients without seizures it was 69.7% with febrile convulsions and 55.8% with epilepsy. Some 80.6% of patients with unclassified generalized motor seizures, 11.5% of those with infantile spasms, 2.9% of those with secondary generalized epilepsy other than infantile spasms, 46.4% of those with partial seizures, and 25.0% of those with hemiconvulsive seizures were finally placed in group I. The percentage of patients without seizures was 81.4, 33.0, 34.4, 57.7, and 100%, respectively. As has been suggested, among the first-year epilepsies, a subgroup with a more favorable prognosis may exist. Further studies regarding the etiology, ictal EEGs, and effectiveness of treatment and long-term prognosis of these cryptogenic benign infantile convulsions are needed to provide a firm basis for understanding convulsive disorders in the first year of life.