Elderly patients with intermediate-or high-grade non-Hodgkin's lymphoma have a worse outcome than those who are younger than 60 years. It has been shown that aggressive combination chemotherapy is poorly tolerated in older patients resulting in a subsequent decrease in dose intensity. A phase II trial was conducted with mitoxantrone, prednimustine, and vincristine (NSO) in this group of patients. NSO consists of mitoxantrone 12 mg/M 2 intravenously on day one, vincristine 1.4 mg/M 2 intravenously on day 1 (maximum dose of two mg), and prednimustine 100 mg/M 2 orally once a day for four days. NSO was repeated every 21 days. Thirty-six patients were able to be evaluated. There were 18 males and 18 females with the median age of 71 (range 60-85). NSO was well tolerated and nonhematological toxicities were uncommon. More than 80% of the patients received 90% or greater of the intended dose. The complete response rate was 60.6% and partial response was 21.8%. At 60 months the Kaplan-Meier estimate of progression-free survival was 47.9% (standard error 8.6%) and actual survival was 40.6% (standard error 8.8%). There were no differences in outcome between those with performance status (PS) of zero or one and those with PS > 1. NSO is well tolerated by elderly patients including those with PS > 1. These results compare favorably with other combinations in elderly patients with aggressive non-Hodgkin's lymphoma. Am.