Two cases of TS associated with brain tumors had severe psychomotor retardation and early onset of long-term intractable convulsions, compared with cases without tumors. In one case, the tumor was partially cystic and progressed rapidly. Immunohistochemical studies of neuron specific enolase, glial fibrillary acidic protein and myelin basic protein revealed differences in positivity between cell types and between cases. These results suggested that the origin of the tumor cells could be variably differentiated cells.