A method for two‐dimensional electrophoretic separation of myelin proteins is presented. The first dimension consists of isoelectric focusing of lyophilized and delipidated membrane proteins, solubilized in a mixture of the nonionic detergent Triton X‐100, the zwitterionic detergent CHAPS, 9 M urea and carrier ampholytes, and incorporated into a slab before separation. Subsequent discontinouous sodium dodecyl sulfate‐polyacrylamide gel electrophoresis was performed ny moulding the isoelectric focusing slab gel with its supporting glass plate into the stacking gel. This method proved to give highly reproducible results since mechanical forces and thus the risk of stretching, folding or rupture of the isoelectric focusing slab gel is minimized. Furthermore, by immunoblotting. the positions of myelin‐associated glycoprotein and 2′,3′‐cyclic nucleotide 3′‐phosphodiesterase were established with specific antibodies. Copyright © 1990 Verlag Chemie, GmbH