N aney J. Rothwell ytokine neurobiology is now a hot topic! Only a few years ago C most neuroscientists were only dimly aware of cytokines and knew little about their function or biological importance. Cytokines, now a huge collection of polypeptides with diverse activities, were until quite recently, studied by those interested in the immune system, inflamma- tion, cancer or infection in peripheral tissues, and did not feature in neuroscience. For example, less than five years ago virtually no refer- ence was made to cytokines in any of the numerous abstracts at the American Society for Neuroscience annual meeting. This situation has now changed dramatically. In an article in early 1995 (Hopkins and Rothwell), we reported an exponential increase in articles on cytokines and the nervous system within the previous year and it seems that this publication frenzy is continuing. There are sev- eral reasons for such interest in cytokines and the nervous system. Firstly, the field of neuroimmunology (or psychoneuroimmunologyl psychoneuroendocrinology) has developed considerably in the past five years. Thus the importance of interactions between the nervous, im- mune and endocrine systems in responses to disease, injury and stress is now recognized. These bidirectional communications have been mirrored by active dialogue (and even collaboration) between neuro- scientists and immunologists. Cytokines form a critical part of neuroimmune interactions.