An immunoaffinity capillary electrophoresis (ICE) system for rapidly quantifying recombinant cytokines in human body fluids has been developed. Cytokines within biological fluids were labeled with a red light emitting fluorochrome and injected into the capillary. Selected cytokines were captured by immobilized antibodies on the internal surface of the capillary, and held while unbound materials were purged. The cytokines were then eluted electrophoretically in acidic buffer. Individual cytokine peaks were detected by on-line laser-induced fluorescence detection coupled to a computerized fiber-optic spectrometer, and analyzed by integration of the eluted peaks. The comparison of the results of ICE to routine assays used for these cytokines demonstrates that ICE provides a fast and accurate procedure for defining these cytokines in complex biological samples. Immunoaffinity separations can be used for any material to which a specific antibody can be raised, making this procedure applicable to a wide range of molecules of biomedical interest.