The autopsy findings on a 60-year-old man with progressive disturbances of gait, presenile dementia and incontinence, showed Lafora bodies in numerous ganglion cells of the cerebral cortex and in many nuclei of the brain stem. Histochemical analysis of the Lafora bodies revealed the presence of a polysaccharide-protein complex containing phosphate groups. The case closely resembled the one described by Suzuki et al. It is suggested that this type of presenile dementia may be a presenile form of Lafora disease.