This paper reports on the clinical, neurophysiological and neuroradiological characteristics of a patient with Down syndrome unusually associated with tuberous sclerosis. In particular, epilepsy is investigated in detail and its polygraphic study and etiopathological factors are discussed. The most interesting findings are those related to the presence of a structural abnormality of the rolandic-parietal cortex, bilaterally, in the form of pachygyria.