Fourteen previously treated patients with relapsed or refractory poor-prognosis non-Hodgkin's lymphoma were given chemotherapy regimens containing high doses of cytosine arabinoside alone (seven patients) or with an anthracycline or amsacrine (seven patients). Five patients achieved a complete remission and two patients had a partial remission. The durations of remission, however, were short (median, 3 months; range, 2-6 months). Toxicities included conjunctivitis, photophobia, stomatitis, dermatitis, cerebellar dysfunction, diarrhea, nausea, vomiting, liver dysfunction, and severe myelosuppression. Recovery of an absolute granulocyte count greater than 500/microliter and an untransfused platelet count greater than 20,000/microliter required a median of 31 (range, 28-35) and 30 (range, 27-43) days, respectively. Six patients died with recurrent or residual disease before bone marrow recovery. Younger age, good performance status, and a previous complete remission were predictive of a good response. High-dose cytosine arabinoside has major myelotoxicity but significant activity in some patients with poor-prognosis non-Hodgkin's lymphoma.