OBJECTIVES: In the current study, we hypothesized that beraprost would: 1) improve treadmill exercise performance and quality of life; and 2) decrease rates of ischemic events in patients with intermittent claudication. BACKGROUND: Previous trials with beraprost sodium, an orally active prostaglandin I2 analogue, in the treatment of claudication in patients with peripheral arterial disease (PAD) have been inconsistent. METHODS: Patients with intermittent claudication (n = 897) were randomized to receive either 40 μg three times a day of beraprost with meals (n = 385) or placebo (n = 377) in a double-blinded manner for one year. The primary efficacy parameter was treadmill-measured maximum walking distance, as assessed at three and six months after randomization. Secondary efficacy parameters included treadmill-measured pain-free walking distance and change in quality of life. RESULTS: There was no significant improvement in maximum walking distance in the beraprost group (16.7%) as compared with the placebo group (14.6%, p = NS). Administration of beraprost did not improve the pain-free walking distance (p = NS between treatment groups), and there was no improvement in the quality-of-life measures between the treatment groups. The incidence of critical cardiovascular events was 7.3% in the beraprost group and 11.4% in the placebo group (p = NS). There was a significant reduction in the combination of cardiovascular death and myocardial infarction in the beraprost group (p = 0.01). CONCLUSIONS: Despite previous investigations suggesting efficacy, these results indicate that beraprost is not an effective treatment to improve symptoms of intermittent claudication in patients with PAD. The potential benefit of beraprost on critical cardiovascular events would require confirmation in a larger prospective investigation.