We surveyed 522 consecutive patients from a dementia clinic to assess duration of driving after disease onset and instances of unsafe motor vehicle operation in the preceding 6 months. Among the 333 patients licensed to drive at the onset of dementia, the median duration of driving after onset was 28.6 months. Patients with a clinical diagnosis of Alzheimer's disease drove significantly longer than those with other dementia syndromes. Of the 93 patients still driving at the time of the survey, approximately one third were reported to have had at least one form of unsafe motor vehicle operation in the past 6 months, including 21 patients with motor vehicle accidents. Motor vehicle accidents were associated with use of prescription medications with sedative properties and with lower subjective ratings of the patient's driving ability by the informant.