Ion chromatography (IC) has been developed for the simultaneous analysis of cations and anions in the water, food, atmosphere, etc. Chromatography can yield the precise and reproducible data if the experimental condition is kept constant. In the present studies, the major cations and anions in the tap water were determined with the technique of IC. A Dionex ICS-2000 ion chromatograph with a Dionex gradient pump, eluent degassing module and conductivity detector was used. Cations were separated on a CS12 A ion-exchange column, with a CG-12 A guard column, and detected after suppression with CSRS 300 cation electrical self-regenerating suppressor. Anions were separated on an AS 11 HC ion-exchange column, with an AS 11 HC guard column, and detected after suppression with an ASRS 300 anion electrical self-regenerating suppressor. The results indicated that the technique of IC was suitable for the rapid, precise and accurate determination of major cations and anions in the tap water samples. In addition, the acceptable detection limits were obtained for all the cations and anions, and the time of analysis was significantly shortened with the technique of IC.