Micellar electrokinetic chromatography was used to study the behavior of quinine, propranolol, bilirubin, biliverdin dimethyl ester, and xanthobilirubin methyl ester in single and binary bile salt micelle systems comprised of glycocholic acid and glycocleoxycholic acid. Micelle systems studied had total bile salt concentrations in the range of 10-33 mm with molar ratios of 1:0, 2:1, 1:1, 1:2, and 0:1 glycocholic acid: glycodeoxycholic acid. A pH 8.5 phosphate-borate buffer system was used. For all analytes except bilirubin, the smallest migration factors were found in glycocholic acid solutions and the largest in glycocleoxycholic acid solutions. Intermediate migration factors were found for all compounds except bilirubin in the binary bile salt systems. Bilirubin behaved uniquely with its largest migration factors in the binary bile salt mixtures.