Abstract: Objective: To investigate the expression of hypoxia inducible factor- 1 α (HIF-1 α) and vascular endothel ial growth factor (VEGF) at the mRNA and protein levels in esophageal squamous cell carcinoma (ESCC) cell lines EC-109 and CaEs- 17at different time points under hypoxic conditions. Methods:Human ESCC cell lines EC-109 and CaEs- 17 were cultured in vitro and the expression of HIF- 1 α and VEGF proteins under hypoxic condi tions was detected wi th immu-nofluorescence. Real-time PCR was used to detect HIF-1 α and VEGF mRNA expression. Results: The mRNA and protein expression levels of HIF-1 α and VEGF in EC-109 and CaEs- 17cells were increased under hypoxic conditions. The in -crease in VEGF mRNA and protein expression appeared later than that of HIF-1 α under hypoxic condi tions, and HIF-1 α mRNA and protein expression was higher than VEGF mRNA and protein expression at8 hours after induction of hypoxia. Conclusion: Hypoxic conditions can upregulate the mRNA and protein expression of HIF-1 α and VEGF in ESCC cel ls. The increase in VEGF expression appears later than that of HIF- 1α.