A rapid and sensitive method for determining the anticholinergic agent, proglumide, in plasma by high-performance liquid chromatography is described. Samples were acidified with hydrochloric acid and extracted with chloroform. The dried extract was resolved in chloroform and chromatographed on an adsorption chromatographic column using a mobile phase of chloroform-methanol (24:1) on a high-performance liquid chromatograph equipped with a UV absorbance detector (240 nm). The detection limit for proglumide was 0.05 microgram/ml.