Avemar, a wheat germ preparation with immunomodulant and antimetastatic activity, was applied simultaneously with cytostatic drugs of different modes of action, in vitro and in vivo, in order to find out whether this simultaneous administration exerts an antagonistic or a synergistic effect on the viability of cell cultures, tumor growth, and survival of animals, inoculated with a transplantable mouse tumor (3LL-HH). In vitro, Avemar did not influence the effect on the viability of MCF-7, HepG2, or Vero cells, exerted by Dacarbazine, 5-fluorouracyl, or Adriblastina. In vivo, Avemar, combined with Endoxan, Navelbine, and doxorubicin, did not prevent the tumor growth inhibitory effect of the cytostatic drugs. The combination of Avemar with the cytostatic drugs did not increase the toxicity of the cytostatic compounds, and did not exert any toxic effect. Avemar may be administered together with cytostatic drugs, without the risk of increasing toxicity or decreasing antiproliferative activity.