Alloferons are a group of antiviral and anti-tumor peptides primarily isolated from insects and stimulating cytotoxic activity of natural killer cells in mammals including mice and humans. Alloferon-1 is currently used in the treatment of persistent viral infections; however its anti-tumor potential needs further preclinical assessment. Here we evaluate alloferon-1 anti-tumor activity in DBA/2 mice grafted with syngenic P388 murine leukemia cells. Alloferon-1 was applied alone or in combination with conventional cytotoxic chemotherapy (a mixture of cyclophosphamide, doxorubicin and vincristine). Alloferon-1 monotherapy demonstrated moderate tumoristatic and tumoricidal activities comparable with low dose chemotherapy. When alloferon-1 and the cytotoxic drugs were combined in a regime of pulse immunochemotherapy the combination anti-tumor activity evidently exceeded that of the treatments applied individually.