Endothelin-1 has been associated with development of hypoxia-related pulmonary hypertension and vascular endothelial growth factor (VEGF) with protection from this complication. In Chuvash polycythemia, homozygous germline von Hippel-Lindau (VHL) 598C-> T leads to up-regulation during normoxia of hypoxia inducible factor-1a and several hypoxia-controlled genes including erythropoietin and VEGF. We postulated that endothelin-1 and pulmonary artery pressure may be elevated in Chuvash polycythemia. Systolic pulmonary artery blood pressure was estimated by Doppler echocardiography and plasma concentrations of endothelin-1, VEGF and erythropoietin were determined in 14 patients with Chuvash polycythemia and 14 controls. Results. Plasma endothelin-1 (p= 0.010), VEGF (p= 0.022) and erythropoietin (p< 0.0005) concentrations and Doppler-estimated systolic pulmonary artery pressures (p< 0.0005) were higher in the patients while systolic systemic blood pressures were lower (p= 0.001). Five (36%) patients and no controls had mild pulmonary hypertension defined as systolic pulmonary artery pressure (c) 35 mmHg. Among the patients with Chuvash polycythemia, the trends of association of estimated pulmonary artery pressure with plasma concentrations of endothelin-1 (R=+ 0.236), VEGF (R=-0.389) and erythropoietin (R=+ 0.220) were not statistically significant. Estimated systolic pulmonary artery pressure and plasma concentrations of endothelin-1 and VEGF are increased in patients with Chuvash polycythemia patients. The lack of significant associations of estimated systolic pulmonary artery pressure with plasma endothelin-1 and VEGF levels could conceivably be due to the small sample size. Further studies are indicated, especially in view of the reported efficacy of endothelin-1 receptor blockers in treating hypoxia-associated pulmonary hypertension.