A new thallium(I) selective electrode based on dibenzyldiaza-18-crown-6 as membrane carrier was successfully prepared. The electrode exhibits a near-Nernstian response for Tl+ ions over a wide concentration range from 1.0 ´ 10-5-1.0 ´ 10-1 M at 25 oC, and was found to be selective, precise and useable within the pH range 4.0-11.0. The electrode was successfully used as an indicator electrode in potentiometric titration of thallium ions.