The influence of six aminoguanidine derivatives on the process of humoral and cellular immunogenesis was examined. The obtained results can be presented in the following items: 1. Strong action inhibiting the primary humoral response was found in mice of Balb/c strain where the decrease of PFC number in spleen was from 34.8% to 96.7%; only the second preparation (D-mannose-ylidene-aminoguanidine) (HCl) caused a significant increase of PFC number and thus, on the contrary, exerted the action stimulating the humoral immunological response. 2. Among the examined preparations only three (third, fourth and fifth) showed the action inhibiting MIF production (the decrease within 30-50%) and only these three preparations caused a clear prolongation of allograft survival in the pattern: Balb/c-recipient, C3H-skin graft donor. 3. The clear decrease of the number of lymphocytes in peripheral blood was found (within 40-60%) as a result of administering aminoguanidine derivatives. 4. Synergism was not found to occur when administering jointly ALS and aminoguanidine derivatives, with the aim of prolonging allograft survival or inhibiting MIF production.