Background. We hypothesize that angiogenic factors are altered by the interaction between neuroblastoma cells and host tissues. Materials and methods. Human Chang hepatocytes and human neuroblastoma cells are cultured separately and in a noncontact, coculture system. Immunostaining for VEGF is performed on the cells. ELISA is used to detect vascular endothelial growth factor (VEGF), basic fibroblast growth factor, and interleukin-8 in the conditioned media. Human umbilical vein endothelial cells (HUVEC) are cultured with standard medium (control) and hepatocyte, neuroblastoma, and coculture conditioned media. After 48 and 72 h, cells are counted to determine proliferation. Finally, VEGF-blocking antibody is added to the HUVEC cultures with the conditioned media. Results. VEGF is markedly elevated in the coculture medium compared to the media from hepatocytes or neuroblastoma grown alone [412.2 ± 52 vs 235 ± 35 or 74.5 ± 28.5 (pg/10 6 cells), P < 0.05]. Other growth factors are almost undetectable in any of the media. Im-munostaining for VEGF in the cocultured hepatocytes is decreased by almost 50%, but VEGF immunostaining is increased fourfold in the cocultured neuroblastoma cells. A significant increase in cell proliferation is seen at both 48 and 72 h when HUVEC are cultured with the coculture media. Cell proliferation is blocked with the addition of anti-VEGF antibody. Conclusion. The interaction of neuroblastoma with hepatocytes results in an increased production of VEGF. It stimulates endothelial cell proliferation and may enhance the tumor's metastatic potential in an autocrine fashion. © 2001 Academic Press.