The preoperative and postoperative PVEP in 79 eyes of 45 patients with three types of congenital namely lamellar cataract, nuclear cataract and total cataract was studied. The results showed that visual acuity of patients who could be cooperatively examined was improved significantly after operation. The examination of PVEP revealed that more abnormal waveforms were found in total cataract group before operation. P1 latencies of low and medium spatial frequencies (140', 70', and 35') became much longer in total cataract group than those in lamellar and nuclear cataract groups. The abnormal changes of P1 latency of high spatial frequency (17.5') showed similar in three groups. It is suggested that time for surgery should be based on visual function in the different types of congenital cataract. The total congenital cataract and unilateral cataract should be extracted as early as possible.