Normal aortic valves are known to be metabolically active, yet the route of oxygen delivery is uncertain. Although diffusion from their surface is the presumed source, the presence, distribution and importance of the valve's vascular bed is unclear. Vessels were found in 32/45 (71%) of porcine aortic valve cusps after filling the coronary circulation with Aquablack. Vessels were found predominantly in the basal third, extending in from the commissures. No difference in vascularization pattern was noted between the left, right or non-coronary cusps. The presence of a vasculature suggests the metabolic activity of the cusp is greater than can be supported by diffusion from the cusp surface. The absence of functioning vessels could help to explain the failure of cryopreserved implants and may play a role in the durability problems of bioprosthetic valves. The role of this intrinsic circulation will also have to be considered with the advent of tissue-engineered valves.