Routine and research techniques are outlined for the analysis of bile acids in serum. The basis of these techniques is the use of liquid-solid extraction and liquid-gel chromatography coupled with the measurement of bile acids by gas chromatography using high resolution glass capillary columns and mass spectrometry which provides increased sensitivity compared with conventional methods of measurement. Problems associated with the isolation and purification of bile acids from serum are discussed and rapid and flexible methods for their metabolic profiling are described. The advantages and applicability of these procedures are illustrated with examples of profiles of bile acids in the serum from normal subjects, patients with liver disease and a patient with an ileal resection.