A novel plastic poly (vinyl chloride) membrane electrode based on pethidine-reineckate ion-association complex as ion-exchange site for determination of pethidine hydrochloride in injections and tablets was described, in which the plasticizer was dibutyl phthalate. The linear response covered the range of 1x10-5~1x10-3 M drug concentration with a slope of 53.50 mV/decade. The practical pH range was 2~8. The lower detection limit was 4.36x10-6 M. There was negligible interference from a number of inorganic and organic cations and some common drug excipients. The proposed electrode had been successfully applied to determine pethidine hydrochloride in tablets and injections. The results were correlated well with those obtained by the United States Pharmacopoeia standard procedure