Contrary to early speculations of TNF-α cytotoxic action on malignant cells in animal tumour models, it is now accepted that TNF-α is weakly cytotoxic to malignant cells.32 Our in vitro results support this, as no cytotoxic effect of TNF-α alone or in combination with electric pulses on SA-1 fibrosarcoma cells was observed. This evidence concerns the gene TNF and fibrosarcoma.