Background: DNA Topoisomerase IIα (Topo IIα) is a nuclear enzyme whose expression levels are related to tumor cell growth and to resistance to anticancer chemotherapy. Materials and Methods: Topo IIα expression was assessed immunohistochemically in 60 surgical specimens of 47 consecutive oligodendroglioma patients. Expression levels were correlated with the MIB-1 proliferation index and with patient outcome. Results: Topo IIα expression ranges from 0.3 to 40.1% and is significantly associated with MIB-1 staining. There is a weak trend to a higher expression of Topo IIα in anaplastic oligodendrogliomas (p = 0.08). Topo IIα expression is not related to patient outcome. Conclusion: Topo IIα expression appears to serve as a marker for tumor growth in human oligodendrogliomas. The widely varying expression levels of Topo IIα in oligodendroglioma suggest this enzyme could be used for targeted selection of patients for Topo IIα-interfering chemotherapy.