A new method has been devised to enable the determination of halide anions by isotachophoresis. This method uses an electrolyte system that employs indium(III) as a counter-ion to manipulate the effective mobilities of sample species by means of complexation reactions. This new procedure successfully enabled the simultaneous determination of the halide ions chloride, bromide, and iodide when a 12 mmol L(-1) nitrate-based leading electrolyte containing 3.5 mmol L(-1) indium(III) at pH 3.0 was used.