AbstractA synergistic increase in the cytotoxic effects of recombinant human tumor necrosis factor (rH-TNF) and anti-cancer drugs was demonstrated in vitro. The cytotoxicity of rH-TNF against L-M cells in combination with Mitomycin C (MMC), Adriamycin (ADM), Cytosine arabinoside (Ara-C), Actinomycin D (ACD), Daunomycin (DM), Cisplatin (CDDP), Vincristin (VCR), and 5-Fluorouracil (5FU), based on the concentration necessary for 50% inhibition of cell growth (IC50), was 4 to 347 times as high as that of rH-TNF alone. The results suggest that combination therapy including rH-TNF and anti-cancer drugs may be of value in the treatment of malignancy in human patients.