Abstract: Background: Hypoxia-selective tumor therapy has great importance since hypoxic environment makes the tumor refractory to radiation and antineoplastic agents. The compounds with hypoxic cell sensitizing property have been evaluated in association with various therapeutic strategies and some of them are found to be operational. Sanazole (a nitro-imidazole compound) a well-known hypoxic radiation sensitizer, has been attested for its hypoxia-selective activity at molecular level. In the present study, the effect of Sanazole on the transcription of major genes responsible for hypoxia-associated tumor growth such as hif-1α, vegf and egfr in tumor cells under in vitro and in vivo conditions was investigated. Methodology: The transcriptional expressions of these genes were studied by quantitative real-time PCR. The levels of nitric oxide in the tumor cells and tissues were studied by Griess test. Results: The transcription of these genes were up-regulated in hypoxic tumor cells while it was down regulated significantly in the cells treated with Sanazole compared to the control (normoxic) cells. The same pattern of expression was observed in tumor tissues of animals treated with Sanazole. Conclusion: Thus, the study revealed the effect of Sanazole in hypoxia-induced tumor growth which makes this compound useful for targeting cytotoxic drugs to hypoxic solid tumor.