The extensively studied patient N.A. has had a severe verbal memory deficit since 1960, when he sustained a stab wound to the brain with a miniature fencing foil. His amnesia occurs in the absence of any other known cognitive defect. Recent CT scans have localized a lesion in the left dorsal thalamus of this patient in a position corresponding to the dorsomedial nucleus; there is no radiographic evidence of other damage in the diencephalon or cerebral cortex. The dorsomedial thalamus may be critical in the neuropathology of diencephalic amnesia and, in humans, may be required for normal memory functions.