Studies of automobile accident frequency among drivers with AD have yielded conflicting results about the risk of accidents. To develop a practice parameter regarding driving and AD the authors performed a systematic review of the literature. The authors identified well-designed, controlled studies of driving and AD using the National Library of Medicine's MEDLINE database. The authors also compared the relative rates of crashes and other performance measurements of driving ability in the populations studied. Driving was found to be mildly impaired in those drivers with probable AD at a severity of Clinical Dementia Rating (CDR) 0.5. This impairment was no greater than that tolerated in other segments of the driving population (e.g., drivers age 16 to 21 and those driving under the influence of alcohol at a blood alcohol concentration BAC < 0.08%). Drivers with AD at a severity of CDR 1 were found to pose a significant traffic safety problem both from crashes and from driving performance measurements.