The purpose of this study was to develop a screening test of driving knowledge for use with dementia patients and other older drivers. Seventy-five drivers with dementia and 80 non-demented elderly drivers completed a 39-item questionnaire concerning the rules-of-the-road and a Mini-Mental State Examination (MMSE). Using item analysis, 15 items were selected for a screening test. The internal consistency reliability of the test was 0.74, while that of all 39 questions was 0.79. Patient and control means on the test differed significantly (p < 0.001). MMSE scores accounted for only 16 percent of the variance in driving knowledge scores in the dementia patients. Results suggest that it is possible to develop a knowledge-based driving instrument that can successfully be administered to patients with diagnoses of mild to moderate dementia. Drivers with dementia demonstrated significantly poorer knowledge of driving regulations than the control group. However, the final score on the driving instrument was not well predicted by the MMSE, suggesting that direct assessment of driving knowledge is important to driving assessment.