The clinical and pathologic findings were reviewed in 20 patients who had cancer and neurological symptoms associated with thromboembolic disease affecting multiple organs. Sixteen of the patients had nonbacterial thrombotic endocarditis. Large-vessel occlusions were present in nine patients. Microvascular occlusions and microinfarcts were present in 14 of the 16 patients with nonbacterial thrombotic endocarditis and in all four without it. The clinical picture may be either that of acute episodes of focal neurological dysfunction or that of a more slowly evolving diffuse organic brain syndrome. These clinical profiles are often superimposed. This disorder is a disseminated intravascular coagulation syndrome of which nonbacterial thrombotic endocarditis is a frequent manifestation. While nonbacterial thrombotic endocarditis may be a source of cerebral emboli in some of these patients, cerebrovascular occlusion also may evolve independently.