The second phase of the study, which began in August, 1995, is a blinded, prospective, randomized, placebo-controlled trial of folic acid treatment of elevated plasma homocysteine in the same patient population. Folic acid treatment has been demonstrated to result in normalization of elevated plasma homocysteine. The treatment trial addresses the clinical question: Do patients with symptomatic peripheral vascular disease and elevated plasma homocysteine treated with folate have less frequent/rapid progression of peripheral vascular disease than patients with symptomatic peripheral vascular disease and elevated plasma homocysteine treated with placebo? Although the second phase is described as a clinical trial, the Surgery and Bioengineering Study Section describes it as clinical research, not an NIH-defined Phase III trial.