Forty-five patients with intermittent claudication were first treated with placebo tablets for 3 months and then randomly allocated to double-blind therapy with either suloctidil or placebo for 6 months. Walking distance improved significantly in both groups during the 3 months of placebo treatment. During the 6 months of double-blind treatment with a further significant improvement occurred only in the placebo group when all patients were analyzed. However, when patients who stopped for reasons unrelated to claudication such as angina and exhaustion during repeated walking tests were eliminated, only suloctidil-treated patients improved significantly. The evolution of leg flow and distal pressure was similar in the two treatment groups whether all legs or only legs with abnormal flow and pressure values were considered. By contrast, when the analysis was limited to legs with claudication pain, a significant improvement occurred only in the suloctidil-treated group. These findings suggest that suloctidil may improve the claudication symptoms of patients with chronic arterial obstructive disease and in particular the perfusion of legs experiencing claudication pain. However, the clinical significance of this improvement appears limited.