The efficacy of pentoxifylline (PXF) in severe intermittent claudication was studied comparing PXF and placebo. Patients were randomized into two treatment plans: PXF (2400 mg, four 600-mg tablets daily) or equivalent placebo was administered for 10 days. The exercise protocol associated with treatment was conducted under supervision. Skin flux (RF) was measured at rest and after 1 minute of exercise (AEF = after exercise flux; 3 km/hr, 12% inclination) with laser Doppler. PO2 and PCO2 were measured at the dorsum of the foot. All 20 included patients completed the study. The two groups were comparable. In the PXF group there was a significant increase in RF, AEF, and in PO2 (p<0.05); PCO2 was decreased (p<0.05). There were also changes in the placebo group, significantly lower than those observed in the PXF group (p<0.05). In conclusion high-dose PXF treatments improved all microcirculatory parameters in subjects with short-range claudication even with a short period of treatment.