Recently, three patients with hemiconvulsion-hemiplegia-epilepsy syndrome who underwent callosotomy were monitored for more than four years. All patients had atrophy of the right brain hemisphere with left hemiparesis and seizures. Two cases were probably the result of traumatic intracranial hemorrhage and one was due to an unknown cause. Wada tests were done in cases 1 and 2, which showed spared motor function of the atrophic hemisphere, supporting the choice of callosotomy instead of hemispherectomy. Patient 1 had atypical absence seizures and asymmetric generalized tonic seizures before surgery, the latter of which decreased by about 60% after callosotomy. Patient 2 had simple partial seizures of the motor type and complex partial seizures, the latter of which were also induced by touch (somatosensory-induced reflex epilepsy). This patient's complex partial seizures disappeared completely, but the simple partial seizures remained unchanged. Patient 3 had generalized tonic seizures, simple partial seizures of the sensory type and complex partial seizures. After surgery, the frequency of the generalized tonic seizures decreased more than 90%. The simple partial seizures of the sensory type remained unchanged. There were two new types of seizures after surgery, simple partial seizures of the motor type and brief generalized myoclonic jerks. All patients had significant reductions in numbers of seizures of more than 50%.