A method has been developed for measuring serum conjugated bile acids by HPLC. Serum samples, to which the internal standard is added, are purified by a solid phase procedure and injected on a reverse phase C18 column. Elution is accomplished by means of a flow gradient and peaks are detected at 198 nm. The detection limit ranges between 0.05 and 0.20 mumol/l for different analytes; between-day precision (CV 5.8%), working linear range (up to 50 mumol/l) and recovery (87%) were established. Comparison of the results obtained with HPLC, enzymatic and immuno-enzymatic methods gave high correlation coefficients. The method was applied for diagnostic purpose to a group of subjects suffering from various liver diseases. Also, 106 healthy workers, not occupationally exposed to known or potentially hepatotoxic agents, were studied in order to establish reference values for use in biological monitoring of chronic low level exposure to solvents. The method has the advantage of a more simple procedure compared to previously reported HPLC methods and appears to be well suited for routine use in toxicological and clinical test laboratories.