The identification of cytokines, a class of intermediate molecular weight, intercellular regulatory proteins, and an understanding of their function has been facilitated tremendously by the use of recombinant DNA technology. Following closely upon these developments has come the ability to detect and quantify cytokines in clinical and biological samples, in large part made possible by the use of specific and sensitive immunoassays using anti-cytokine antibodies. Cytokine detection with antibody-based techniques is particularly useful because so many of these factors have overlapping, parallel, or counter-regulatory bioactivities and it is extremely difficult to distinguish and measure them in complex mixtures on the basis of biological activity alone, Therefore, both neutralizing antibodies in bioassay systems and cytokine immunoassays of complex samples are required (Mosmann & Fong 1989). In the first part of this review, we outline the general strategy we have followed for preparing a large panel of anti-mouse and human cytokine monoclonal antibodies (mAb) and setting up cytokine immunoassays. While there is a general consensus that many of the frequently produced cytokines such as IL-1, TNF, IFN-y, IL-6, and IL-8 may be general inflammatory mediators, see for example (Dunn 1991), definitive links between the detection of specific cytokine patterns and the pathogenesis of particular diseases are in the early stages of being understood. The eventual elucidation of such cause-and-