This work describes the development and fabrication of a selective polymeric membrane electrode for iodide ion based on a metallophthalocyanin complex with a titanium(IV) atom at the center (as an oxo-titanium, Ti=O, group), phthalocyaninatotitanium(IV) oxide (PcTiO), as a sensing carrier. The potential response characteristics of the electrode were investigated by changing the type of plasticizer as well as the amounts of the carrier and different lipophilic ionic site additives in the sensing membrane. It is shown that the membrane electrode incorporated with 2-nitrophenyl octyl ether as the plasticizer and hexadecyl trimethylammonium bromide as the appropriate cationic additive exhibits enhanced potential response toward iodide over other anions tested. Over the period of this study, the resulting electrode based on PcTiO displayed a stable near-Nernstian slope approaching -58.9 mV decade(-1) with a linear response spanning at least 5 orders of magnitude in concentration from 1.0 x 10(-1) to 9.2 x 10(-7) mol L(-1) and a detection limit of 8.5-10(-7) mol L(-1). The preferential potential response to iodide may be attributed to the unique recognition of carrier PcTiO in the organic membrane phase for iodide in solution. Under laboratory conditions, the present electrode also works well in partially nonaqueous media. The excellent analytical features of the proposed electrode could lead to its successful application in determining the end point in electrometric titration of iodide with Ag(+) and the direct potential determination of iodide concentration in wastewater and drug preparations.