Separation of single and double stranded DNA molecules by capillary gel electrophoresis has a rapidly growing interest. Similar to the polyacrylamide slab gel based separation methods, in capillary gel electrophoresis, the peak/band spacing usually decreases with the increasing size/length of the DNA molecule. Additionally, employing the regularly used Tris-borate buffer system, fronting peaks are often obtained. By the application of an electrolyte step gradient during capillary gel electrophoretic separation of dsDNA molecules, the apparent peak shape can be improved and the required analysis time decreased.