A differential puts ancxlic stripping peak of indium appeared at -0.52v (Vs Ag/AgCl) in a solution of 1.65N KBr -0. 05N HCL -0.02% NH2OH . HCL. Under this condition, In can be determination within the range 0.0004一O.O2µgml-1. The detection limit was 0.04 ppb. The presence of 30-fold excess of Cd and 100 -fold excess of Pd only causes negligible interference. The interference caused by other ions is prevented by the preliminary chromatographic separation.