A HPLC Assay was developed to identify and measure the metabolite of acrylamide, mercapturic acid, N-Acetyl-s-(propionamide)-cysteine (APC) in urine. O-phthalaldehyde (OPA) was utilized as a precolumn derivatizing agent in the assay. This derivative was isolated with a good selectivity by high performance liquid chromatography (HPLC) employing reversed phase ODS columns. The quantitation of the mercapturic acid derivative was reproducible and with a detection limit of 1 pmol. The average coefficient of variation for the runs carried out on the same day was approximately 4.6% at the range of 80-160 mumol.L-1 of APC, and the mean analytical recovery from urine samples was 94%. The metabolite of urine of workers exposed to acrylamide was identified as N-acetyl-s-(propionamide)-cysteine by HPLC chromatography and fluorescence scan and HPLC-Mass spectra. All results were identical with the authentic synthesized compound.