The clinical and pathologic findings in 42 autopsy proved cases of cerebral infarction from cancer-associated non-bacterial thrombotic endocarditis were reviewed. Carcinoma of the lung was the most common malignancy. Most patients had disseminated cancer, but in six patients, the condition was stable or in remission, and six patients had localized cancer; two patients were not known to have cancer until neurologic symptoms developed. Neurologic symptoms were focal, suggesting stroke in 18; diffuse, suggesting metabolic encephalopathy in nine; and mixed in five. Neurologic signs were often the only evidence of thromboembolism. The definitive diagnostic test was cerebral angiography showing multiple arterial occlusions. Anticoagulation with heparin appeared to help some patients and did not promote brain hemorrhage. Early diagnosis and vigorous treatment of non-bacterial endocarditis may prevent severe neurologic disability.