The treatment of relapsing or refractory high-grade malignant non-Hodgkin lymphoma (NHL) following CHOP chemotherapy remains a challenge for the clinician. In this study, 29 patients with relapsing or refractory high- or refractory low-grade malignant NHL received a combination of mitoxantrone 12 mg/m2 i.v. on days 1-2, cytarabine 100 mg/m2 i.v., b.d. d 1-2, etoposide 100 mg/m2 i.v. d 1-3 and prednisone 100 mg/m2 orally d 1-3 (ENAP). An overall response rate of 55% encouraged us to use ENAP alternated with conventional CHOP chemotherapy in 45 previously untreated NHL patients (35 with high-grade and 10 with "aggressive" low-grade malignant NHL). All patients responded with a complete remission rate (CR) of (27%) and a partial remission rate (PR) of 73% after only one course of ENAP. After a median number of 3.5 ENAP/CHOP courses, the CR and PR rate was 69 and 22%, respectively. Myelosuppression was pronounced and fever of unidentified origin and documented infections followed 59% of all cases given ENAP courses. In the last 19 previously untreated patients mitoxantrone was given at a dose of 10 mg/m2 on d 1 and cytarabine 100 mg i.v., b.d. during d 1-2. Nonhematologic toxicity was mild. We conclude that this novel chemotherapy program is effective both as first-line and salvage treatment in patients with high-grade malignant NHL. Furthermore, ENAP appears clinically to be partly non-cross resistant with CHOP chemotherapy. The dose-limiting toxicity is myelosuppression. The combination should be explored as primary therapy in combination with other chemotherapy or radiotherapy programs.