The recognition of the anaplastic variant of oligodendroglioma is difficult, since it is not easy to identify histological prognostic factors. Among the latter, vascular productive changes have been inconsistently put in relation with survival. In 95 cases of operated oligodendrogliomas, endothelial cell hyperplasia, microvascular proliferations and capillary density were studied by histological and immunohistochemical methods. Capillary density was evaluated on CD31-stained sections by a grid of 100 squares placed in the ocular of the microscope. Statistical analysis was performed in order to compare these parameters with survival. A nodular growth pattern was observed more frequently among tumor grades 3-4 than among tumor grades 1-2. Endothelial cell hyperplasia was more frequent in nodular growth pattern, but it did not correlate with survival. The highest capillary density was found in nodular growth pattern, but it did not correlate with survival as well. Microvascular proliferations correlated with survival only in univariate, but not in multivariate analysis. Age, extent of surgical removal, year of surgery, post-operative Karnofsky score and MIB-1 LI remained associated with survival, as observed in a previous study.