Ten patients with non-Hodgkin's lymphomas (NHL), six untreated and four with previous chemotherapy, were treated with TA-077, a new derivative of nitrosourea. Partial remission was observed in three untreated cases (30%) of NHL [Case 1: 71-year-old female with B cell lymphoma/diffuse small cell type, Case 2: 79-year-old male with T cell lymphoma/diffuse large cell type, and Case 3: 64-year-old female with adult T cell leukemia lymphoma (ATLL)]. Remission durations were as follows: Case 1; 33 days, Case 2; 38 days and Case 3; 14 days. Side effects were transient anorexia (40%), nausea & vomiting (30%), liver dysfunction (10%) and delayed hematological toxicities (80%). Hematological toxicities consisted of leukocytopenia (80%), thrombocytopenia (60%) and anemia (20%). Our study suggests that TA-077 is a useful agent as one of the drugs used in combination chemotherapy against NHL, since it was effective for refractory T cell malignancies such as ATLL.