Abstract This paper investigates the use of a non-cross-linked polymer gel as a separation matrix for sodium dodecyl sulfate (SDS) capillary gel electrophoresis of proteins. The method employs a polyacrylamide coated capillary filled with a polyethylene oxide-gel buffer solution. A standard seven-protein mixture was chosen for the evaluation of coating stability and reproducibility. It was found that the coating is stable for more than 400 runs with a 1 M HCl wash between each run. The hydrophilic nature of polyethylene oxide also allows high resolution and high efficiency for all protein peaks. The linear plot of log M r vs. mobility demonstrates a pure sieving mechanism of polyethylene oxide matrices. The molecular masses of twenty-nine standard proteins determined by SDS capillary gel electrophoresis are in good agreement with those obtained from the SDS polyacrylamide gel electrophoresis (PAGE) slab gel method. The capability to replace the gel after each run allows improved run-to-run and batch-to-batch reproducibility. The relative standard deviation (R.S.D.) in migration time of 19 injections of the seven-protein standard mixture, with the 190 injections of crude fetal calf serum in between, falls in the range of 0.351 to 0.453%. The application of this technique for the separation of proteins in chicken egg white and bovine milk is demonstrated.