TNF is a cytokine whose diverse actions are dependent on the local microenvironment. As a member of the cytokine network, TNF plays an important role in infection and inflammation, but excessive and deregulated production can contribute to disease processes. Likewise in malignant disease, TNF may have a role in cancer therapy and contribute to host response against tumours, but it may also be involved in the progression and spread of the cancer. In experimental models, recombinant TNF can induce significant haemorrhagic necrosis, localised to the tumour vasculature and specific tumour immunity. Although the historical background and preclinical data are promising, systemic therapy with TNF in human cancer has proved highly toxic and is inactive against all tumour types so far tested. Local therapy, particularly isolated limb perfusion, has resulted in complete and long lasting tumour regressions with necrotic activity confined solely to the tumour vascular bed. However, in several animal models, TNF contributes to malignant progression and there is evidence that TNF may have autocrine or paracrine actions in human ovarian cancer.