Early phase II study of MST-16[4,4-(1,2-ethanediyl) bis (1-isobutoxycarbonyloxy-methyl-2, 6-piperazinedione], a derivative of ICRF-154, on malignant lymphoma was conducted by multi-institutional cooperative group. MST-16 was administered orally at doses of 1,600 mg/body/day for 5 days or 1,200 mg/body/day for 10-14 days, mainly. The number of registered and evaluated patients were 29 and 28, respectively (Hodgkin's disease 3 patients and non-Hodgkin lymphoma 25). Twenty-seven of 28 patients had received prior chemotherapy and/or radiation therapy. Of 28 evaluable patients, overall response rate (CR + PR) was 32.1%. In high-dose administration group, the response rate was not significantly high. The response rate seemed to be high in patients who were treated repeatedly (number of courses greater than 3). Major side effects observed were myelosuppression and gastro-intestinal disorders which were reversible in a rest period. Myelosuppression seemed to be severe in high-dose administration group. This study indicated that MST-16 was a useful agent against malignant lymphoma including primary resistant or relapsed patients, and that the recommended regimen for a late phase II study was considered to be 1,600-2,400 mg/body/day for 5-7 days repeatedly with a pause of several days. Furthermore, the study should be considered at the dose of 3,200 mg/body because half cases administered at this dose showed some response.