Tumor angiogenesis is an important process for several kinds of tumor, especially, during its angiogenic switch. The present study was aimed to investigate the dynamical process of tumor neocapillarization in Hepatocellular carcinoma cells implanted nude mice model. Male BALB/c nude mice (20-25 g) were used. After the implantation of a dorsal skin-fold chamber, the Hepatocellular carcinoma cells (HepG2) (30 microl of 2 x 10(6) cells) were inoculated into the upper layer of the skin within the chamber (HepG2-group), while the shammed control group (Sham-group) was received a normal saline. Intravital fluorescence videomicroscopy was performed to monitor the tumor neocapillary on days 7 and 14 post-inoculation by intravenous injection of 0.1 ml rhodamine B isothiocyanate-labeled dextran (0.5%). Based on the recorded videoimages, the tumor microvascular networks were measured using a digital image analysis. The neovascular density and configuration were represented in terms of microvascular density index (MVDI) and neovascular bifurcation ratio (BR). The MVDI levels of HepG2-group were significantly increased on day 7 and 14 compared to the age-matched Sham-group. The increase in MVDI agreed with the increase in the BR. In conclusion, our dorsal skin-fold chamber technique with intravital fluorescence videomicroscopy and digital image analysis was most useful to monitor the neovascular network for quantitatively evaluating the progression of tumor angiogenesis in terms of MVDI and BR values.