In this study, a new poly(vinyl chloride) (PVC) membrane electrode for La3+ ion based on paraldyhed phenyl hedrazon as an electroactive material was prepared.This electrode revealed good selectivity for La3+ over a wide variety of other metal ions. Effects of experimental parameters such as membrane composition, nature and the amount of plasticizer, the amount of additive on the potential response of La3+ electrode were investigated. The electrode exhibited a Nernstian slope of 20.0±1.0mV per decade of La3+ over a concentration range of 1×10-7 to 1×10-1M of La3+ in the pH range 3.8–8.0. The response time was about 30 s and the detection limit was 7×10-8 M. The electrode couldbe used for at least one month without a considerable divergence in potential. The proposed electrode was used for the determination of lanthanum in a standard solations andwas successfully applied as an indicator electrode for potentiometric titration of La3+ with EDTA.