The present invention relates to ligands which bind to human tumour necrosis factor alpha (TNF) in a manner such that upon binding of these ligands to TNF the biological activity of TNF is modified. In preferred forms the ligand binds to TNF in a manner such that the induction of fibrin deposition in the tumour and induction of endothelial procoagulant activity of the TNF is inhibited; the binding of TNF to receptors on endothelial cells, tumour regression, cytotoxicity and receptor binding activities of the TNF on tumour cells are unaffected. The ligand is preferably an antibody, F(ab) fragment, single domain antibody (dABs), single chain antibody or a serum binding protein. It is preferred, however, that the ligand is a monoclonal antibody or F(ab) fragment thereof.