Nonbacterial thrombotic endocarditis (NBTE) is characterized by the deposition of thrombi on undamaged heart valves and by the increased frequency of associated arterial embolic events in patients with chronic debilitating diseases. Fifteen subjects diagnosed by necropsy of nonbacterial thrombotic endocarditis (NBTE) were studied to evaluate the general features, associated diseases, arterial embolic events, distribution and characteristics of histologic lesions. The most common underlying disease was neoplasm, which was present in 10 cases. Of these, 6 were adenocarcinomas, 3 hematological, and the remaining case was a bladder carcinoma. Other associated diseases included amyloidosis, MELAS syndrome, and sepsis. In most cases peripheral arterial embolic events were detected (9 cases). The central nervous system and the lung were involved in 7 cases (78%), heart and kidneys in 5 cases (56%), and spleen in 4 cases (44%). Other involved organs included pancreas, thyroid gland, testicles, meninges, liver and adrenal glands. The left valves were predominantly involved. The mitral valve in eight cases and the aortic valve in six cases. All cases with right involvement had the antecedent of central venous catheterization. Subendothelial fibrosis was a common histological finding which revealed the chronicity of the disease.