Nonbacterial thrombotic endocarditis (marantic endocarditis) has been considered by many authors to be an incidental postmortem finding in cachetic individuals and to have no clinical significance.1-4 There have been occasional references to the possibility of embolization from the valvular vegetations.5-9 Allen and Sirota8 and also Angrist10 have studied the problem of nonbacterial thrombotic endocarditis (NBTE) in some detail and consider this entity to be of prime importance in the initiation and progression of bacterial endocarditis. Angrist and Marquiss9 presented evidence relating the lesion to a high incidence of infarcts in brain, coronary arteries, kidney, spleen, and extremities. In a recent study stressing the clinical significance of the lesions, MacDonald and Robbins11 confirmed this phenomenon by demonstrating a high incidence of embolic infarctions of clinical importance. Such embolization was occasionally directly contributory to the patient's death. The purpose of this paper is to emphasize the