A simplified, rapid and inexpensive extraction procedure for the determinaticn of the antiarrhythmic drug disopyramide and its main mctabolitc mono-N-dcsalkylated disopyramidc in strum by high-pcrformante liquid chromatography has been developed. The analysis uses ullraviolct detection at 254 nm, and a 5 jtm reversed-phase column with a mobile phase of water-tricthylaminc-acctonitrilc-PIG-B8 reagent. Scrum extraction is performed with dichloromethane and 1 &f sodium hydroxide. p-Chlorodisopyramide is used as internal standard.Recovery rates were 94.5% (SD. 5.7%) for disopyramide, 96.5% (S.D. 2.2%) for mono-N-desalkylatcd disopyramidc and 97.9% (S.D. 2.8%) for the internal standard.