Pulmonary thrombendarterectomy was performed in 32 patients (14 men and 18 women; mean age 38 +/- 15 years) with thromboembolic pulmonary hypertension (New York Heart Association stage III: n = 22; stage IV: n = 10). The preoperative arterial pO2 averaged 59 +/- 11 mm Hg; pulmonary vascular resistance (PVR) and mean pressure (MPAP) were increased to 1,045 +/- 430 dyn.s.cm-5 and 53 +/- 12 mm Hg, respectively. The perioperative death rate was 22% (7 of 32). In the 25 survivors the pulmonary hypertension was reduced to a PVR of 194 +/- 75 dys.s.cm-5, MPAP of 28 +/- 6 mm Hg. Subsequent re-examination in 15 patients (NYHA stage I: n = 14, stage II: n = 1) after a mean of 17 +/- 5 months demonstrated an arterial pO2 averaging 92 +/- 6 mm Hg and, in 14 patients, echocardiographically normal right-ventricular volumes and function. The primary success was confirmed in eight patients by haemodynamic measurements. These data indicate that thrombendarterectomy can effectively treat the increased PVR in most patients at all stages of the disease.