The aortic valve owes its strength and durability to a network of collagen fibers within the leaflets. However, the pattern of these fibers and their role in valve function is not well understood. We imaged and quantified the macroscopically visible pattern of collagen fibers in seven porcine aortic valves with particular attention to measuring this pattern in the unstrained leaflet. We then used a structural finite element model of the aortic valve to study the effect of the observed collagen pattern on the configuration of the loaded valve. Results showed that collagen is oriented oblique to the free edge over much of the leaflet in its unstrained state, and simulations suggest that this architecture plays an important role by enabling adequate valve leaflet coaptation. Simulation results were validated by comparison with images of a porcine aortic valve under load.