To determine whether motion sensitivity varies with age, we measured motion discrimination in visual normals 25 to 80 years of age and found that motion thresholds increased linearly with age and were approximately two times higher in those 70 to 80 years old than in participants under thirty. This increase was not attributable to pupil size or retinal image distortion, but probably reflects neurodegeneration in the primary visual pathway. We compared the motion sensitivity of patients with senile dementia of the Alzheimer type (SDAT) with results from a subset of the visual normals of similar age. In SDAT patients, there were significant threshold elevations, which were more pronounced in the patients with more severe dementia. These findings confirm previous reports of visual system involvement in SDAT and indicate motion testing may reveal preclinical visual system involvement in SDAT.