Neovascularization is an important factor in the prognosis of brain tumor and many angiogenetic factors have been evaluated for prognostic significance. Among them, basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF) are known as potent angiogentic factors and mitogens. We evaluated seven cases of grade II brain astrocytoma. Four, group A, was diagnosed as anaplastic progression at their second operation, and three, group B, did not. Using monoclonal antibodies to bFGF and VEGF in paraffin embedded tissue from first operation, their immunoreactivity and differences between two groups were examined. The growth fractions of these tumor were also measured by Ki-67 monoclonal antibodies (MIB1). Immunostaining for bFGF in tumor cells were observed in both nuclei and cytoplasm, and for VEGF, mainly observed in the cytoplasm. Mean cell count number +/- standard deviation per high power field in each were as follows: 1) for bFGF, 20.08 +/- 6.38 in group A and 0.87 +/- 0.90 in group B (P < 0.01), 2) for VEGF, 43.75 +/- 17.09 in group A, and 0.8 +/- 1.06 in group B (P < 0.05) and 3) for the proliferation index with Ki-67 antibodies, 3.20 +/- 0.81 in group A and 0.77 +/- 1.03 in group B (P < 0.05). This data supports the assertion that angiogenetic factor such as bFGF and VEGF may contribute to progressive change of astrocytoma by tumor angiogenesis.