The 56 patients who got epoprostenol increased the distance they could walk in 6 minutes from 270 to 316 meters. The 55 patients who received only usual therapy could walk 240 meters at the start of the study but only 192 meters at the end. Four epoprostenol patients and 5 usual therapy patients died during the course of the study. Frequent side effects of epoprostenol were jaw pain, diarrhea, nausea, and loss of appetite. Depression also occurred, but less commonly. In addition, patients who got epoprostenol had important side effects, including infection (4 patients) and bleeding (3 patients), that were related to the intravenous tube.