Peripheral arterial occlusive disease (PAOD), coronary artery disease (CAD), and cerebrovascular disease (CVD) are all manifestations of atherosclerosis or atherothrombosis, and therefore it is not surprising that the three conditions commonly occur together. Knowledge of the magnitude of co-existing cardiovascular disease and its prognosis is essential for the physician treating IC so that he can treat the local disease in its systemic context. The prevalence of CAD in patients with IC is 40% to 60%, although this may be asymptomatic and increases with the severity of the PAOD. Not surprisingly, the converse is also true; among individuals with CAD, the prevalence of PAOD is higher than in non-CAD individuals. The link between PAOD and CVD seems to be weaker than that with CAD, but again up to 60% of claudicants have some evidence of CVD. The prevalence of patients with CVD increases as the ABPI decreases. The evidence available from all of the relevant studies suggests that approximately 60% of patients with PAOD will have significant disease in the cardiac or cerebral circulation, and approximately 40% of patients with coronary disease or significant cerebral circulatory disease also will have PAOD.