Protein adsorption onto the inner walls of capillaries is a widely recognized problem in the separation of proteins by capillary electrophoresis. Chemical modification of the wall has been an effective method for suppressing this effect. The performance of an epoxy based hydrophilic coating has been evaluated under different experimental conditions. High efficiency separation of proteins (up to 200,000 theoretical plates per meter) was achieved using this coating. The recoveries of both cationic and anionic proteins were very high (over 90% for several positively charged proteins) on this capillary coating. The influence of both pH and potential on efficiency, resolution and peak capacity were examined.