A phase II trial of pyrazofurin, alone and in combination with trifluorothymidine, was carried out in patients with advanced non-Hodgkin's lymphoma. None of the 19 patients evaluable for response had complete or partial remissions but 14 had minor regressions. Toxicity, consisting primarily of myelosuppression and stomatitis, was of moderate severity. These studies suggest that pyrazofurin, alone or in combination with trifluorothymidine, is of limited utility in advanced non-Hodgkin's lymphoma.