The NINCDS-ADRDA criteria for the clinical diagnosis of probable Alzheimer disease (AD) state that "gait disturbances at the onset or very early in the course of the illness make the diagnosis of Alzheimer disease uncertain or unlikely," yet there have been few studies documenting the validity of the statement. We therefore reviewed all cases of pure autopsy-proven AD in the Ramsey Brain Bank to determine how frequently an abnormal gait was noted at time of presentation. Any reported gait disturbance was considered an abnormal gait. Only cases for which medical records were available documenting the patient's presentation for dementia were included. Cases were excluded if any other pathology was present that may have contributed to the patient's dementia or to a gait disorder, if neuroleptic medication had been used, or if there was a preexisting gait disorder. Clinical dementia severity at time of presentation was graded as mild, moderate, or severe per DSM-IIIR criteria. Of the 95 cases that met study criteria, none of the 36 patients with mild dementia were reported to have had an abnormal gait. Sixteen percent of the patients with moderate and 32% with severe dementia had gait abnormalities reported. This study confirms the statement regarding gait in the NINCDS-ADRDA criteria.