Radioimmunoassay (RIA) of cholic and chenodeoxycholic acid was compared to a total bile acid determination with 3 alpha-hydroxysteroid dehydrogenase (3 alpha-HSD) and a gas liquid chromatographic (GLC) determination of individual bile acids. When sera from patients with increased bile acid concentration were analysed the results indicated a good correlation between GLC and the other methods. Analysis of sera from healthy subjects indicated a good correlation between GLC and RIA. There exists no correlation between RIA and 3 alpha-HSD when serum bile acids were analysed in healthy subjects in part due to the presence of varying amounts of secondary bile acids.