To determine the natural history of intermittent claudication 112 patients were followed for a minimum of 5 years and a median period of 82 months. Thirty-seven patients (33 per cent) died during the study period. Myocardial infarction (44 per cent) and cerebrovascular disease (28 per cent) were the most common causes of death. Overall mortality rate was 8, 23 and 40 per cent, at 2, 5 and 8 years respectively. Initial ankle-brachial pressure index (ABPI) correlated with subsequent death. With an initial ABPI less than 0.5 death occurred in 20, 50 and 69 per cent at 2, 5 and 7 years respectively, compared with 5, 16 and 24 per cent respectively for those with an initial ABPI greater than or equal to 0.5 (P less than 0.0001). Of the survivors only 21 per cent had worsening claudication and 13 per cent progressed to critical ischaemia. Arterial bypass for limb salvage was required in eight patients and four limbs were lost during the study period. ABPI identifies a subgroup of claudicants with an extremely high risk of death from coronary and/or cerebral pathology. In this subgroup an aggressive approach to the correction of atherosclerotic risk factors, rather than emphasis on the peripheral vascular problem alone, may improve survival.