Objective: A classic physiologic response to systemic hypoxia is the increase in red blood cell production. Hypoxia-inducible factors (HIFs) orchestrate oxygen-sensing machinery and hypoxic cell metabolism. Recent works suggest that mutation of the HIF oxygen-sensing pathway plays a key role in the pathogenesis of the erythrocytosis. In the present study, the probable role of the polymorphic HIF-1 alpha variants, C1772T (P582S) (rs11549465) and G1790A (A588T) (rs115494657), which are known to enhance transcriptional activity, were evaluated in the etiology of the polycythemia.