3-Hydroxypropylmercapturic acid [3-OHPrMCA, S-(3-hydroxypropyl)-N-acetyl-L-cysteine] was quantitatively measured by high-performance liquid chromatography (HPLC) in the urine of rats given allylamine.HCl (5, 25, 50, 100 and 150 mg kg-1), acrolein (13 mg kg-1), allylalcohol (64 mg kg-1), allylchloride (76 mg kg-1), allylbromide (120 mg kg-1), allylcyanide (115 mg) and cyclophosphamide (160 mg kg-1) by gavage in water. 3-OHPrMCA was measured by HPLC in 24-h urine collections; the lower detection limit was 1.25 micrograms or 5.6 nmol ml-1. Various doses of allylamine resulted in 3-OHPrMCA excretion at a fairly constant percentage of the dose, ca. 44-48% at 0-24 h and 3% at 24-48 h, indicating rapid metabolism through glutathione conjugation in the first 24h. Similarly, 3-OHPrMCA was recovered in the urine of rats given acrolein (78.5%), allylalcohol (28.3%), allylchloride (21.5%), allylbromide (3.0%), allylcyanide (3.7%) and cyclophosphamide (2.6%). These data indicate that 3-OHPrMCA can be used as a marker of exposure to allylic and other compounds that lead to the metabolic formation of acrolein.