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 chemotherapeutic 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 toxicity have been observed.