Nonbacterial thrombotic endocarditis is the most prevalent endocarditis at autopsy. It is a clinically important cause of arterial embolisation. Often it is observed in association with malignancy (mainly gastrointestinal adenocarcinomata), severe infections and other fulminant acute disease processes. A deranged or damaged valvular surface and clotting disorders are important pathogenic factors. The valvular vegetations are pathologically characterized by a bland, fibrin-platelet thrombus; they usually affect the mitral and aortic valve. Neurologic events are the most common clinical manifestations, but any organ may be involved by emboli. The association of venous and arterial thromboses and pulmonary thromboembolism underscores the pathogenetic role of hypercoagulability in the development of nonbacterial thrombotic endocarditis. The clinician must be a vigilant observer in order to make the antemortem diagnosis. If possible, the underlying process should be treated; anticoagulation therapy with heparin sometimes is helpful.