For protein quantitation in gels or blotting membranes, chemiluminescence (CL) offers the advantages of a substantial improvement of detection limits. Easy-to-use CL-chemicals and specific probes such as antibodies conjugated to enzymes, e.g. alkaline phosphatase (AP) may be used in combination with a newly developed luminometer. CL was found to have low detection limits and a linear relation between relative light units (RLU) and the concentration of the antibody enzyme complex present over a wide concentration range. Measurements of the immunoglobulin IgE in dot blots and in blots after sodium dodecyl sulfate (SDS) electrophoresis under nonreducing conditions in agarose gels are described.