Four hematopoietic in vitro cell lines (Hodgkin derived cell lines L428 and L540, Burkitt's lymphoma line BJAB and the lymphoblastic lymphoma line of T-cell type L735) were transplanted into nude mice (NMRI nu/nu) intramuscularly and intracerebrally as well. Tumor bearing mice were treated with intraperitoneal administration of Cyclophosphamide, Adriamycin, Etoposid and Vindesine. Therapy results in both systems were proven by Student's t-test and significances were compared. Resistance and sensitivity of cell lines tested in the i.c.-system were largely in accordance with the i.m.-system. Best results of treatment were achieved with the T-lymphoma line L735 treated with Cyclophosphamide and Etoposid. Cyclophosphamide induced complete remission of i.m. tumors in several cases whereas in the nude mouse brain the L735 cell relapsed and showed a more aggressive growth and diminished drug sensitivity.