To examine the effect of transcatheter arterial embolization (TAE) of liver tumors on hypoxia-inducible factor-1α (HIF-1α) expression in the residual viable tumor,a total of 30 New Zealand White rabbits implanted with VX2 liver tumor were divided into 2 groups. TAE-treated group animals (n=15) were subjected to TAE with 150-250 μm polyvinyl alcohol particles. Control group animals (n=15) underwent sham embolization with distilled water. Six hours,3 days or 7 days after TAE,the animals were sacrificed,and samples of tumor and adjacent normal liver tissue were harvested. Expression of HIF-1α protein was examined immunohistochemically. Real-time PCR was performed to examine the HIF-1α mRNA levels. Our results showed that HIF-1α protein was expressed in the VX2 tumors but not in the adjacent normal liver tissue. The HIF-1α-positive tumor cells were located predominantly at the periphery of necrotic tumor regions. The mean levels of HIF-1α protein were significantly higher in TAE-treated tumors than those in control tumors (P=0.002). Among the three sacrificing time points,the difference in increase in HIF-1α protein was significant between the two groups at the sacrificing time point of 6 h and 3 days after TAE (P=0.020,P=0.031,respectively),whereas no significant increase was noted 7 days after TAE (P=0.502). In contrast,although HIF-1α mRNA was expressed in TAE-treated and control VX2 tumors,there existed no significant difference in the HIF-1α mRNA level between the two groups (P=0.372). It is concluded that TAE of liver tumors increases the expression of HIF-1α at protein level in the residual viable tumor,which could be attributed to hypoxia generated by the procedure.