BACKGROUND: Peripheral arterial disease (PAD) affects up to 12% of adults older than 50 years of age. Conventional therapies have only modest effects in improving symptoms. OBJECTIVE: To examine the effects of angiotensin-converting enzyme inhibition on walking ability in patients with PAD. DESIGN: Randomized, double-blind, placebo-controlled trial initiated in March 2003 and completed in January 2005. SETTING: The Alfred Hospital, Melbourne, Australia. PARTICIPANTS: 40 older adults with symptomatic PAD and no history of diabetes or hypertension. INTERVENTION: 10 mg of ramipril (n = 20) or placebo (n = 20) once daily for 24 weeks. All patients completed the trial. MEASUREMENTS: Pain-free and maximum walking time were recorded during a standard treadmill test, and the standard Walking Impairment Questionnaire was administered. RESULTS: After adjustment for the baseline pain-free walking time, mean pain-free walking time after ramipril treatment was 227 seconds (95% CI, 175 seconds to 278 seconds; P < 0.001) longer than that after placebo treatment. Similarly, maximum walking time improved by 451 seconds in the ramipril group (CI, 367 seconds to 536 seconds; P < 0.001) but did not change in the placebo group. Ramipril improved the Walking Impairment Questionnaire median distance score from 5% (range, 1% to 39%) to 21% (range, 12% to 58%; P < 0.001), speed score from 3% (range, 3% to 39%) to 18% (range, 8% to 50%; P < 0.001), and stair-climbing score from 17% (range, 4% to 80%) to 67% (range, 38% to 88%; P < 0.001). No adverse events were reported. LIMITATIONS: The sample size is modest, and the strict inclusion criteria limit the applicability of the results to patients with claudication and infrainguinal disease and those without diabetes. CONCLUSION: Ramipril improved pain-free and maximum walking time in some adults with symptomatic PAD.