Two-dimensional (2-D) immunoelectrophoresis, also known as crossed immunoelectrophoresis, is a particularly useful technique for the quantitation of mixtures of proteins and the analysis of the composition of protein mixtures. The method consists of two sequential electrophoretic steps: 1. The first dimension, during which the protein mixture to be analyzed is separated by electrophoresis in an agarose gel. 2. The second dimension, during which the separated proteins are electrophoresed at right angles into a freshly applied layer of agarose containing a predetermined amount of antibody.