Optimal dose and timing of CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone) chemotherapy for aggressive non-Hodgkin lymphoma (NHL) is still an unresolved issue. We assessed whether dose intensifications with cyclophosphamide and doxorubicin might improve outcome in younger patients with intermediate-risk aggressive NHL. Previously untreated patients were assigned to receive either 8 courses of standard CHOP (n = 239) or 6 courses of intensified (I)-CHOP (n = 238). Although there was a tendency in favor of I-CHOP for overall survival (OS), disease-free survival (DFS), and event-free survival (EFS), the differences were not significant. However, although these analyses were not planned, when the intermediate-risk group was divided into low-intermediate- and high-intermediate-risk patients according to the International Prognostic Index (IPI), low-intermediate-risk patients had improved 6-year OS (67% vs 52%; P = .05), DFS (58% vs 45%; P = .06), and EFS (41% vs 30%; P = .21) when they were treated with I-CHOP compared with standard CHOP. On the other hand, high-intermediate-risk patients seem to have no benefit from I-CHOP. Although clinically relevant side effects occurred more often in the I-CHOP arm, treatment-related mortality was similar. These data suggest that I-CHOP might be preferable to standard CHOP in younger patients with low-intermediate-risk aggressive NHL.