The whole-cell mode of the patch clamp technique was used to study Ca²⁺-activated Cl^- current (I_ClCa) in gastric antral myocytes. Extracellular application of caffeine evoked Ca²⁺-activated current. In order to isolate the chloride current from background current, all known systems were blocked with specific blockers. The current-voltage relationship of caffeine-induced current showed outward rectification and it reversed at around E_Cl^-. The shift of reversal potential upon the alteration of external and internal chloride concentrations was well fitted with results which were calculated by the Nernst equation. Extracellular addition of N-phenylanthranilic acid and niflumic acid which are known anion channel blockers abolished the caffeine induced current. Intracellular application of a high concentration of EGTA also abolished this current. Application of c-AMP, c-GMP, heparin, or AIF^-₄ made no remarkable changes to this current. Sodium replacement with the impermeable cation N-methylglucamine or with Cd²⁺ rarely affected this current. From the above results it is suggested that the caffeine induced current was a Cl^- current and it was activated by intracellular Ca²⁺.