A mean increase in the 6-minute walk test of 44.7 meters from a baseline mean value of 329 meters vs. a change of -7.4 meters from a baseline mean value of 324 meters in the placebo group (no data imputation for death or missing values) was observed in the subgroup of 49 patients with primary pulmonary hypertension receiving treatment of inhaled iloprost for 12 weeks (46 patients in the placebo group).