Clinical and electroencephalographic studies were performed to elucidate the characteristics of epilepsy in severely handicapped children. The subjects were 56 severely mentally and physically handicapped children whose ictal seizures were documented by simultaneous EEG-VTR monitoring. Seizure types were infantile spasms in 17 (30.4%), atypical absence in 5 (8.9%), myoclonic seizures in 3 (5.4%), generalized tonic-clonic seizures in 2 (3.6%), secondary generalized partial seizures in 11 (19.6%), and undetermined in 4 (7.1%). Epilepsy types were also classified by the ictal seizure types and clinical courses: West syndrome in 27 (48.1%), Lennox-Gastaut syndrome (LGS) (at onset) in 5 (8.9%), partial epilepsy in 13 (23.2%) and others (at onset) in 11 (19.8%). Among 29 cases with West syndrome, 22 (81%) developed LGS, and among 11 cases with others group, 64% developed LGS. After all, LGS appeared in 60.7% of all 56 severe epileptic children associated with severe physical and mental handicaps.