This study compares the effects of iloprost, a metabolically stable analog of prostacyclin, or placebo administered by intravenous infusion (6 hrs/day, 6 days/week for 5 weeks) on the healing of ischemic ulcers. Iloprost (0.5-2.0 ng/kg/min) or placebo (comparable volume) are titrated to maximum tolerable dose during initial 3 days of treatment and maintained for the remaining 27 days.