[en] The immunophenotypization, tumorigenicity and immunogenicity of the tumor were characterized. The tumorigenic dose of the fibrosarcoma G5:1:13 for mice C3H/DiSn when administered s.c. is 1x10⁵ per mouse. With this dose, tumors with an average volume of 64 mm³ on day 6 developed; 98-100% mice died on day 120. The phenotype of the fibrosarcoma, which is immunogenic, is MHC-I⁺, HNC-II^-, B7^-, B7.2^-. After administration of irradiated tumor cells (2 doses, s.c., 1x10⁶ per mouse), a tumor developed in none of the animals to which the non-irradiated tumor cells had been administered. The effect of the individual factors was examined. Gamma radiation affected survival of the mice as follows: 2x8 Gy (60%), 4x6 Gy (80%), 5x5 Gy (80%), 3x7 Gy (80%), in positive correlation with the tumor size. The growth was affected similarly by MTP-PE (40%), diclofenac (40%), ibuprofen (40%) and flurbiprofen (30%). When diclofenac was combined with MTP-PE, a surprising strengthening of the tumor growth was observed. This finding is very important in view of the clinical use of MTP-PE and inhibitors of arachidonic acid metabolism in the treatment of tumorous diseases