Immunohistochemistry was performed on paraffin sections from human glioblastoma multiforme and normal brain tissue. Acidic fibroblast growth factor (FGF) was abundantly present in astrocytes from all glioblastomas studied. Basic FGF was found in the matrix surrounding proliferating blood vessels in most of the glioblastomas. In contrast, astrocytes from normal brain did not contain acidic FGF, and perivascular matrix staining was not demonstrated for basic FGF in the normal brain. Both growth factors could be demonstrated in neurons, Purkinje cells, capillary endothelium, and arterial walls in the normal brain. This study implicates both growth factors in the pathogenesis of malignant glioma. Both may be significant mediators of angiogenesis in glioblastoma.