Intramyocardial small vessel abnormalities are not commonly recognized. The best known abnormality is fibromuscular dysplasia involving the sinoatrial or atrioventricular nodal arteries. Small vessel disease has been reported as an isolated cardiac anomaly in individuals with sudden death, and may also be associated with other cardiac conditions including hypertrophic cardiomyopathy and mitral valve prolapse. The nature of the association is unknown, and the mechanism causing sudden death is sometimes obscure. We describe pathological changes of the intramyocardial small vessels of three individuals with sudden death. Abnormalities involved small vessels at different levels. In all the cases, the abnormalities were thought to have caused or contributed to the individual's death. The possible mechanisms of this are discussed.