A therapy consisting of a combination of an anticoagulant and a vasodilator was investigated to determine its effects on the long-term prognosis of primary pulmonary hypertension (PPH). Twenty patients with PPH who had undergone diagnostic catheterization in our hospital were studied. The mean follow-up period after the initial catheterization was 6 years, with the longest follow-up being 24.4 years. Seven patients were treated with warfarin as an anticoagulant, combined with either isoproterenol (3 patients) or nifedipine (4 patients) as a vasodilator (AV group). The remaining 13 patients were not treated (control group). Although there were no significant differences in the physical activity or hemodynamics between the groups, improvement was seen in 43% of the AV group and in only 7.6% of the controls. The 5 year survival rate was significantly higher in the AV group (57% vs 15%; P < 0.05). Hemodynamics were evaluated repeatedly in 8 patients and improvement was seen only in the AV group. These results suggest that a therapy consisting of a combination of an anticoagulant and a vasodilator may improve the long-term prognosis of PPH.