In HCC specimens from 25 patients, the levels of nm23-H1 and H-ras mRNA were analyzed by quantitative reverse transcription-polymerase-chain reaction (RT-PCR). Tumor microvessel density (MDV), the essential factor of microenvironment and proliferating cell nucleus antigen (PCNA), indexes as tumor cell proliferating in its microenvironment are also analyzed by immunohistochemical methods using antibodies against endothelial protein factor VIII related antigen (F8RA) and antibody PC-10. Results show that The MDV and PCNA index in the group with intrahepatic metastasis is remarkably higher than that in without one (p<0.01), but the abundance of nm23-H mRNA is opposite (p<0.01). The abundance of H-ras mRNA shows little difference (p>0.05). MDV index shows directly relationship with PCNA index (p<0.01), the abundance of nm23-H1 mRNA show an inverse one with PCNA index (p<0.05). We conclude that in HCC, tumor in situ microenvironment, especially a deteriorative one, plays an important selective role. The decline of nm23-H1 mRNA abundance implies the increase of highly potential metastatic cancer cells which adapt to their microenvironment.