To define the causal relationship of ischemic cerebral infarction to automobile accidents in hospitalized patients a computerized hospital record search with ICD-9 diagnostic codes 433 and 434 for occlusive cerebrovascular disease, and E810 and E819 for motor vehicle traffic accidents was conducted over a three-year period. Inclusion criteria required patients be identified as the driver of the vehicle and demonstrate computed tomographic (CT) evidence of an evolving cerebral infarction on serial scans. Of 2,844 ischemic cerebral infarctions admitted to the hospital during the study period, four met the selection criteria. In three, stroke was the cause and in one, the result of the accident. When stroke preceded the accident, visual field defect impaired consciousness, and/or loss of motor control were major contributing factors. Head CT, detailed accident scene history, and vascular disease risk factors were most important in determining a cause-and-effect relationship of stroke to the accident.