In this study, we examined the expression of inducible nitric oxide synthase (iNOS) and vascular endothelial growth factor (VEGF) by immunohistochemical staining in 76 tissue sections collected from hepatocellular carcinoma (HCC) patients undergoing hepatectomy. Microvascular density (MVD) was determined by counting endothelial cells immunostained using anti-CD34 antibody. We performed DNA-flow cytometric analyses to elucidate the impact of iNOS and VEGF expression on the cell cycle of HCC. Most of the HCC cells that invaded stroma were markedly immunostained by iNOS antibody. The iNOS stain intensity of the liver tissue close to the tumor edge was stronger than that of HCC tissue, and the strongest was the hepatocytes closer to the tumor tissue. However, iNOS expression in 10 normal hepatic samples was undetectable. VEGF positive expression ratio was 84.8% in iNOS positive expression cases, and the ratio was 35.3% in negative cases. There was significant correlation (P=0.000) between iNOS and VEGF expression. Moreover, iNOS expression was significantly associated with bcl-2 and MVD, but without p53 expression. DNA-flow cytometric analyses showed that combined expression of iNOS and VEGF had significant impact on the cell cycle in HCC. PI (Proliferating Index) and SPF (S-phase fraction) in the combined positive expression of iNOS and VEGF group was significantly higher than that in the combined negative group. The present findings suggested that iNOS expression was significantly associated with angiogenesis, bcl-2 and cell proliferation of HCC.