We describe a new method of immunoelectrophoresis with a continuous gradient polyacrylamide gel in the first dimension and an agarose-dextran gel in the second dimension with one or two layers of antibody. The use of a polyacrylamide gel in the first dimension allows better resolution of lipoproteins than with crossed immunoelectrophoresis using agarose gel in both dimensions. The use of two layers of antibody in the second dimension also enhances the specificity of characterization and the resolution of the separation. Thus, using a layer of anti-apo A-I combined with a layer of anti-apo A-II, three particles containing only apo A-I and three containing both apo A-I and A-II could be separated.