Urinary 3, 4-dihydroxyphenylalanine (DOPA) was extracted with alumina after removal of the fatty substances by shaking with ether-benzene (5 : 2), converted to n-butyl ester with n-butanol-HCl (5N) at 100°for 20 min, trifluoroacetylated with trifluoroacetic anhydride in ethyl acetate and determined by gas chromatography using electron capture detector. The overall recoveries of the added DOPA (50, 75, 100, and 150 ng) from urine (2 ml) were 66.0% ±3.55% (n=8). The pressence of DOPA in normal human urine was confirmed by gas chromatographymass spectroscopy.