Despite limitations associated with the use of protein-based drugs, cytokines / growth factors have proven to be valuable therapeutics in the treatment of a variety of chronic and acute disorders. With the ongoing discovery of novel cytokines, and the recognition of new biological activities associated with existing cytokines, the therapeutic utility of these molecules will inevitably expand. In this article, we review three areas of our research activity that represent distinct phases in the therapeutic exploitation of cytokines. First, we discuss progress on the clinical development of leukaemia inhibitory factor (LIF). LIF, a pleiotropic cytokine, has potent neurotrophic effects and a recombinant human version (AM424) is being developed for the treatment of peripheral neuropathies. Second, we describe progress on the characterisation of a novel member of the vascular endothelial growth factor (VEGF) family. Therapeutic angiogenesis is an emerging approach for the treatment of ischaemic heart and limb disease and the cytokines that regulate angiogenesis, such as members of the VEGF family, are the subject of intense interest. Finally, we describe the discovery of a novel class of intracellular proteins (suppressors of cytokine signaling, SOCS) that may play a key role in the downregulation of cytokine signaling. As key regulators of cytokine signaling these molecules represent an exciting new target for drug discovery.