Treatment for newly diagnosed anaplastic oligodendroglial tumors is controversial. Radiotherapy (RT) alone and in combination with chemotherapy (CT) are the most well studied strategies. However, CT alone is often advocated, especially in cases with 1p19q codeletion. We retrospectively identified 1013 adults diagnosed from 1981-2007 treated initially with RT alone (n 5 200), CT 1 RT (n 5 528), CT alone (n 5 201), or other strategies (n 5 84). Median overall survival (OS) was 6.3 years and time to progression (TTP) was 3.1 years. 1p19q codeletion correlated with longer OS and TTP than no 1p or 19q deletion. In codeleted cases, median TTP was longer following CT 1 RT (7.2 y) than following CT (3.9 y, P 5.003) or RT (2.5 y, P <.001) alone but without improved OS; median TTP was longer following treatment with PCV alone than temozolomide alone (7.6 vs. 3.3 y, P 5.019). In cases with no deletion, median TTP was longer following CT 1 RT (3.1 y) than CT (0.9 y, P 5.0124) or RT (1.1 y, P <.0001) alone; OS also favored CT 1 RT (median 5.0 y) over CT (2.2 y, P 5.02) or RT (1.9 y, P <.0001) alone. In codeleted cases, CT alone did not appear to shorten OS in comparison with CT 1 RT, and PCV appeared to offer longer disease control than temozolomide but without a clear survival advantage. Combined CT 1 RT led to longer disease control and survival than did CT or RT alone in cases with no 1p19q deletion. Ongoing trials will address these issues prospectively. © The Author(s) 2011. Published by Oxford University Press on behalf of the Society for Neuro-Oncology. All rights reserved.