Abstract: Objective: To investigate the effects of hypoxia inducible factor 1α (HIF-1α) antisense oligonucleotides (ASODN) on the expression of HIF-1αand vascular endothelial growth factor (VEGF) in the osteosarcoma cell line MG-63 under hypoxic conditions. Methods: The ASODN and sense oligodeoxynucleotides (SODN) were designed on the basis of the HIF-1αcDNA sequence. The hypoxia culture model was established with a hypoxia incubator. The gene expression levels of HIF-1α and VEGF were observed under different hypoxia culture conditions using semi-quantitative reverse transcription PCR (RT-PCR). The protein level of HIF-1αand VEGF was observed by immunohistochemical staining and Western Blot analysis. Results: Compared with cells in normoxic conditions, cells in the hypoxic environment did not show a significant change in the mRNA level of HIF-1α. However, the protein expression of HIF-1αwas markedly increased in the cells in the hypoxic environment with a direct correlation with the duration of hypoxia exposure and in the SODN hypoxia group. In contrast, VEGF expression was upregulated at both the mRNA and protein levels. After treatment with the ASODN, the mRNA and protein levels of HIF-1αand VEGF were significantly decreased. VEGF activity was strongly associated with the protein level of HIF-1α. Conclusion: Under hypoxic conditions in vitro, HIF-1αantisense oligonucleotides inhibited HIF-1αactivity, which thereby decreased VEGF mRNA level and protein expression.