Enhanced chemiluminescence was applied to detect the binding of monoclonal antibodies to surface antigens on intact cells. The fast and simple assay is performed in the microtiter scale and thus allows for the simultaneous processing of a large number of samples with a sensitivity comparable to conventionally used techniques such as cytometry or Western blot analysis. In two model experiments, we demonstrate (a) the detection of a heterologously expressed cytokine receptor subunit on the surface of suspension cells and (b) the screening of hybridoma clones for the production of antibodies specifically recognizing surface antigens on a tumor cell line. Moreover, the assay is shown to be suitable for the determination of antibody affinities and of antibody binding sites per cell.