Aortic stenosis (AS) is thought to be caused by calcific degeneration of the aortic valve. Clinical observations suggest an association between a left dominant coronary circulation and AS, a situation previously investigated at necropsy and with small observational studies. Mitral regurgitation (MR) and aortic regurgitation (AR) are both disorders with multiple etiologies, but neither has any known association with coronary artery dominance.The coronary angiogram database of a tertiary referral centre was reviewed for consecutive left heart catheter data acquired over a six-year period. The severity of AS was classified by measured pressure gradient (in mmHg) as none (0), mild (30), moderate (30-49), or severe (49). Both, MR and AR were assessed visually by the operator.A total of 1,891 patients was included. In the AS group there was a significant association with a left dominant coronary circulation (p0.0001), and the proportion of patients with left dominance increased with the severity of AS (p0.005). There was no significant association of AR with coronary artery dominance (p = 0.84). MR was associated with a reduced prevalence of left dominance (p0.005).AS was associated with a left dominant coronary circulation, and the incidence of left dominance was increased with the severity of AS, but the opposite situation was true for MR. The reasons for these observations remain unclear.