Ten samples of human hepatocellular carcinoma and three of a laceration injure of the liver (controls) were grafted onto the chick embryo chorioallantoic membrane (CAM) to investigate their possible angiogenic activity. The angiogenic response in pathological and control implants was assessed on histologic sections by a morphometric method, 4 days after grafting. The vascular count in the CAMs treated with the pathological implants was significantly higher compared to control ones and the angiogenic response induced by pathological implants was comparable to that of a well known angiogenic molecule, namely basic fibroblast growth factor. The role played in vasoproliferative response by angio-genic cytokines released by tumor cells, by CAM extracellular matrix and by the perivascular mononuclear cells was supported by this study.