Mitoxantrone (Novantrone, NO) and high-dose cytarabine (Ara-C, AC) have each been shown in monotherapy trials to be active in non-Hodgkin's lymphoma (NHL). In the current study, a combination of the two drugs (NOAC) was administered to 31 patients with advanced NHL refractory to modern sequential chemotherapy regimens. Ara-C was administered at 3 g/m2 as a 3 hour infusion every 12 hours on day 1 (2 doses) and mitoxantrone at 10 mg/m2/day on days 2 and 3. Of the 18 patients with high-grade malignant NHL, six have attained a complete remission (CR) and two, a partial remission (PR). One CR and 5 PRs were achieved among the other 13 patients with intermediate or low-grade NHL. The median time to relapse (TTR) of patients achieving CR was 7 months with a range from 4 to 17 months. Myelosuppression with subsequent infections was the major toxicity of this regimen. The median duration of severe neutropenia (less than 0.5/nl) was 9 days with a range of 0 to 27 days and the median duration of severe thrombocytopenia (less than 20/nl), 5 days with a range of 0 to 35 days. Infectious complications during cytopenia was seen in 45.3% of the courses administered and fever of unidentified origin was seen in 42.3%. About 63% of the patients were hospitalized for intravenous antibiotic or antimycotic treatment. Other side effects were mild and included nausea, stomatitis, and transient tachycardia of greater than 100/min. Thus, this regimen was active in refractory NHL with poor prognosis, and the toxic side effects were not excessive. Evaluation of the activity of this regimen at higher dose levels of Ara-C is warranted.