Anions and cations in mineral water were simultaneously measured by capillary electrophoresis with a chelating agent. Ions studied were chloride, sulfate, sulfite, nitrate, nitrite, fluoride, formate, and acetate for anions, and magnesium, calcium, copper, lead and zinc for cations. They were separated in a fused-silica capillary (50 cm × 50 μm i.d.) filled with 300 mM borate buffer (pH 9.0) containing a cationic surfactant and a chelating agent as the electro-osmotic flow modifier and chelator, respectively. The method was successfully applied to the determination of ions in mineral water.