['Age is one the factors associated with poor prognosis in acute coronary syndromes (ACS) and elderly patients are a high-risk collective with few parameters for mid-term cardiovascular stratification. We aimed to assess the predictive value of ankle-brachial index (ABI) in patients (> 75 years) for 1-year mortality after an ACS.', 'Prospective, observational and multicentre study of ACS patients in whom ABI was assessed during hospitalization.', 'A total of 1·054 patients were included, mean age 66·6 (11·7) years from whom 26·6% were > 75 years. Elderly patients showed more history of cardiovascular disease and higher prevalence of all risk factors, except current smoking. Angiography and revascularization were performed less frequently in the elderly. Patients > 75 years showed higher presence of three vessel coronary disease and received fewer guideline-recommended treatments. Patients who died through the follow-up, mean time 387·9 ± 7·2 days, had lower ABI (0·73 ± 0·24 vs. 0·92 ± 0·22; P < 0·01), also in the elderly patients (0·73 ± 0·24 vs. 0·86 ± 0·23; P < 0·01). Cox regression analysis identified age > 75 years (HR: 2·30; IC 95% 1·26-4·18; P < 0·01) and ABI < 0·90 (HR: 3·58; IC 95% 1·80-7·15; P < 0·01) as risk factors for to 1-year mortality. Mortality was similar in elderly patients with ABI > 0·90 and young patients with ABI < 0·90; the worst prognosis was observed in elderly patients with ABI < 0·90 (HR: 10·01; 95% CI 3·74-27·15).'] Is pathological ankle-brachial index equivalent of advanced age in acute coronary syndromes?