The purpose of this study was to examine the influence of treatment on long-term prognosis of patients with aminorex-induced plexogenic pulmonary hypertension. The study included 104 patients (13 males, 91 females) with an aminorex (menocil) intake between 1966 and 1968. All patients were treated with digitalis and diuretics, 52% received an anticoagulant medication with warfarin after pulmonary hypertension was diagnosed. During follow-up, a second right-heart catheterization was performed in 37 patients with a mean interval of 5 years. The longest mean survival time, 8.3 years, was found in patients treated with anticoagulant medication, compared to the 6.1 years found in the non-anticoagulated aminorex patients. Also, in the 5- and 10-years survival rate, patients with an anticoagulant therapy have shown better results (62.9 vs. 38% and 39 vs. 20%, respectively). Patients who received anticoagulant therapy soon after the onset of symptoms showed a better mean survival (10.9 years) than those who commenced treatment more than 1 year thereafter (mean survival 5.9 years). In 57% of the patients who had a second right-heart catheterization a decrease of pulmonary pressures could be diagnosed. Two-thirds of these patients with pulmonary pressure decrease were under anticoagulant therapy. An improvement in the NYHA-classification was seen in 44.8% of the patients treated with warfarin, in comparison to 22.2% of those who did not receive anticoagulant therapy. Although this study is retrospective, it shows a positive influence of anticoagulant therapy on survival in patients with a history of anorectic drug intake.