Surgical specimens from 165 adults with cerebral astrocytoma were reviewed to establish the prognostic value of histologic factors when studied both individually and in combination. Glioblastomas were excluded. Nine morphologic parameters and 25 clinicotherapeutic factors were correlated with survival. Cell density, endothelial hyperplasia, number of mitoses X 10 high-power field (HPF), and vessel frequency appeared to be highly significant prognostic factors (P less than 0.001). Nuclear polymorphism, microcysts, and vessel size were significant moderately (P less than 0.01). Microcysts, vessel size, endothelial hyperplasia, and number of mitoses X 10 HPF remained significant statistically after a multivariate analysis that also included clinicotherapeutic factors. Survival was similar for astrocytomas with "extensive malignancy" and astrocytomas with only "slight and localized malignancy." Multivariate analysis showed that the presence or absence of malignancy was more important prognostically than the clinical variables (i.e., postoperative Karnofsky status or extent of surgical removal).