Brain invasion prevents complete surgical extirpation of malignant gliomas; however, invasive cells from distant, histologically normal brain previously have not been isolated, cultured, and characterized. To evaluate invasive human malignant glioma cells, the authors established cultures from gross tumor and histologically normal brain. Three men and one woman, with a mean age of 67 years, underwent two frontal and two temporal lobectomies for tumors, which yielded specimens of both gross tumor and histologically normal brain. Each specimen was acquired a minimum of 4 cm from the gross tumor. The specimens were split: a portion was sent for neuropathological evaluation (three glioblastomas multiforme and one oligodendroglioma) and a portion was used to establish cell lines. Morphologically, the specimens of gross tumor and histologically normal brain were identical in three of the four cell culture pairs. Histochemical staining characteristics were consistent both within each pair and when compared with the specimens sent for neuropathological evaluation. Cultures demonstrated anchorage-independent growth in soft agarose and neoplastic karyotypes. Growth rates in culture were greater for histologically normal brain than for gross tumor in three of the four culture pairs. Although the observed increases in growth rates of histologically normal brain cultures do not correlate with in vivo behavior, these findings corroborate the previously reported stem cell potential of invasive glioma cells. Using the radial dish assay, no significant differences in motility between cultures of gross tumor and histologically normal brain were found. In summary, tumor cells were cultured from histologically normal brain acquired from a distance greater than 4 cm from the gross tumor, indicating the relative insensitivity of standard histopathological identification of invasive glioma cells (and hence the inadequacy of frozen-section evaluation of resection margins). Cell lines derived from gross tumor and histologically normal brain were usually histologically identical and demonstrated equivalent motility, but had different growth rates.