Abstract: The potential response behaviour of a chloride doped polypyrrole (PPy) polymer film electrode to chloride ion in solution has been examined. The effect of the polymerisation conditions on the characteristics of the potential response and response mechanism is discussed. A chloride ion-selective electrode based on a conducting PPy polymer film was prepared with a potential response slope of 5860 mV (pCl)1 and a detection limit of 3.5 × 105M of Cl. The optimum conditions for the preparation of the electrode were: pyrrole (Py), 0.050.2 M; LiCl, 0.11 M; scan range for electrochemical polymerisation, 0.51.2 V; polymerisation time, 1030 min; and scan rate, 20100 mV s1. The chemical sensor has a fast response, a low resistance, is easy to prepare and is not susceptible to poisoning.