Résumé : Different types of PVC‐matrix ion‐selective electrodes (ISEs) that respond to the cationic form of zopiclone are described. Four ion‐pairing agents, namely tetraphenylborate (TPB), reineckate (RN), phosphotungstate (PT) and silicotungstate (ST), and different plasticizers are investigated. The best PVC polymeric membrane contains nitrophenyloctylether (NPOE) as plasticizer and zopiclone‐TPB as active material. This electrode exhibits a Nernstian response (60 mV per decade) in the range 1 × 10−2 to 1 × 10−5 M and a fast dynamic response time, this response being not affected by pH between 1.9 and 5.5. Direct potentiometry was used to determine zopiclone in drug formulations using this new zopiclone‐selective electode. The results are comparable to those obtained by differential pulse (DP) and square‐wave (SW) polarographic techniques using both direct and standard addition methods. Copyright © 1994 VCH Verlagsgesellschaft mbH