The expression and implication of vascular endothelial growth factor (VEGF) and matrix metalloproteinase-9 (MMP-9) in residual hepatic tumor cells after lipiodol embolization were investigated. Two weeks after transplantation of VX2 tumor cells into the livers of rabbits, a xenograft model of the human hepatic neoplasm was successfully established. Forty rabbits were randomly divided into control group (n=20) and lipiodol group (n=20). For the control group, 1 mL normal saline was injected through the gastroduodenal artery, whereas 0.3 mL/kg lipiodol was applied for the lipiodol group. One week after embolization, the expression level of VEGF in the plasma was measured by using enzyme-linked immunosorbent assay (ELISA). A three-step immunohistochemical technique (ABC) was employed to detect the protein levels of VEGF and MMP-9 and the quantitative PCR for their mRNA levels was performed in the residual tumor cells. The VEGF in the plasma was significantly higher in the lipiodol group (1.42 +/- 0.29 ng/mL) than in the control group (1.12 +/- 0.21 ng/mL) (P < 0.01). Moreover, the positive rate of VEGF protein in the residual tumor cells was significantly higher in the lipiodol group (62.13%+/- 7.69%) than in the control group (53.16%+/- 9.17%) (P < 0.05). Similarly, the MMP-9 expression in the residual tumor cells was higher in the lipiodol group. The mRNA levels of VEGF (2.9313 +/- 2.4231) and MMP-9 (3.5721 +/- 1.6107) in the lipiodol group were significantly higher than those in the control group (1.5728 +/- 0.9453 and 1.7573 +/- 1.0641, respectively, P < 0.05). Therefore, it was reasonable to speculate that the increased expression of VEGF and MMP-9 in residual hepatic tumor cells and tumor angiogenesis post-embolization would be responsible for the increased metastatic potentiality and invasiveness of these cells.