Background/Aims: The phenotypic and functional characteristics of microvascular endothelial cells derived from human liver cancer (HLCEC) were analyzed in vitro and compared with those of human liver sinusoidal endothelial cells (LSEC). Methods and Results: Flow-cytometric and realtime PCR analysis indicated that expressions of tumor necrosis factor receptor (TNFR) p75,alpha v beta 3 and alpha v beta 5 were increased, while those of TNFR p55 and intercellular-adhesion molecule 1 (ICAM-1) were decreased in HLCEC compared with LSEC. The functional analysis indicated that HLCEC exhibited higher angiogenic ability than LSEC, including proliferation capacity, ability to form capillary-like networks and release of matrix metalloproteinases. In response to tumor necrosis factor, LSEC exhibited a significant dose-dependent cytotoxicity, while HLCEC did not. Moreover, the coagulant and fibrinolytic capacity was increased in HLCEC. In addition, tumor cell adherence was significantly higher on HLCEC than on LSEC, while leukocyte adherence was lower on HLCEC than on LSEC. The cytoadherence of HLCEC was inhibited by antibodies against alpha v beta 3 and alpha v beta 5, and of LSEC by antibodies against ICAM-1. Conclusion: These results indicate that tumor-derived endothelial cells are phenotypically and functionally different from those derived from normal liver tissue. These differences are valuable for understanding tumor angiogenesis and metastasis.