A 52-year-old, right-handed female presented with visuospatial dysfunction including left hemineglect, incomplete Balint's syndrome, and environmental agnosia, together with left-sided motor symptoms such as unskillful movement, dystonic postures, and myoclonus in the left hand, without significant dementia. Symptoms progressed to akinetic mutism prior to her death 10 years after onset of illness. Imaging studies such as MRI, SPECT, and PET studies showed severe, predominantly right-sided involvement of parietal and parieto-occipital areas. The motor signs might originate from the right parietal lesions such as area five or somatosensory area. Neuropathologic studies including immunocytochemistry showed tau-positive neurofibrillary tangles and abundant neuritic plaques with amyloid deposits, confirming the diagnosis of Alzheimer's disease. An analysis of serum apolipoprotein E revealed epsilon3/epsilon3 homozygosity. This case represents a variant of Alzheimer's disease conspicuous for progressive motor signs and visuospatial dysfunction with a striking laterality, reflecting asymmetric parietal involvement. Alzheimer's disease with asymmetric parietal atrophy is difficult to be clinically distinguished from corticobasal degeneration characterized by progressive unilateral motor signs and focal cortical signs.