From March 1991 to April 1992, 44 previously untreated patients with stage II to IV intermediate-grade non-Hodgkin's lymphoma (according to the Kiel classification) were entered in a phase III comparative trial. The objectives of the study were to compare the efficacy and safety of using idarubicin instead of doxorubicin in the combination chemo-therapeutic regimen CHOP (cyclophosphamide, doxorubicin, vincristine, prednisolone). Forty-four patients were randomly assigned to receive either CI(idarubicin)OP or CH(doxorubicin)OP. The study is ongoing and so far no significant differences in complete response rate and (non-)hematologic tox-icity have been observed.