Abstract The process of vascularization of the valves of 18 hearts with features of rheumatic heart disease, which were part of a larger series of 147 hearts from patients who died at the Mulago Hospital, Kampala, Uganda, has been studied using injection, microradiographic, and histological techniques. In mildly diseased atrioventricular valves, small vessels were first seen at the valve ring and along the inflamed endothelial surface of the valve leaflets, but vessels also passed up the chordae tendineae to the lower part of the leaflets. The density of vessels increased with more florid disease and sometimes the capillary-like vessels became thick-walled, but the vascularity diminished as the valves became fibrotic and calcified. In the aortic and pulmonary valves, vessels passed into the cusps mainly from the commissures. These appearances were of value in distinguishing rheumatic heart valves from avascular normal valves and those affected by endomyocardial fibrosis.