An improved procedure for the quantitation of clofibric acid in human serum by high performance liquid chromatography with fluorescence detection was developed. The assay is simple, accurate, reproducible and was validated at the concentrations of 0.3-100 ㎍/㎖ in human serum. Regression analysis for the standard plots obtained from intra-day and inter-days studies indicated excellent linearity(r>0.999) and reproducibility(CV, 3.4-5.0%). The pharmacokinetic profile in human could be obtained over seven times the elimination half-life after a single oral dose of 500㎎ of clofibrate.