Tropane alkaloids, contained in gastrointestinal drugs including Scopolia Extract, were determined using high-performance liquid chromatographic method. Tropane alkaloids in commercial drugs were extracted with 0.5 N hydrochloric acid test solution. This solution was adjusted to pH 10.0 with a strong ammonia solution, extracted with ethyl ether, and separated on TSKgel ODS-120T (4.6 mm i.d. x 15 cm; temperature, 30 degrees C; flow rate, 1.5 ml/min; detector, UV 210 nm) with a mixture of 1/15 M sodium phosphate buffer (pH 2.5) and acetonitrile (68:32) containing 12 mM sodium dodecyl sulfate. The contents of atropine in the gastrointestinal drugs were 0.25-0.34 mg (coefficient of variation = 0.20-2.61%) a day.