The present study was designed to evaluate the effects of simultaneous ethanol administration (10%, v/v), and restraint stress (2 hrs/day for 5 day) on serum electrolytes. This restraint stress decreases serum concentration of Na(+), K(+), Ca(2+), phosphorus, and chloride. Ethanol treatment also decreased Na(+), K(+), Ca(2+), phosphorus, and chloride concentration. The decrease in Ca(2+) and phosphorus levels was greater for ethanol-treated restrained than water-treated restrained rats. Ethanol did not affect serum Mg(2+) while it was increased in restrained water-treated rats. Ethanol-treated restrained rats exhibited less serum Mg(2+) than ethanol-treated unrestrained or water-treated restrained rats. Possible mechanism involved in restraint or ethanol-induced changes of electrolytes is discussed. In conclusion, the result of this study suggest that alteration of serum electrolyte caused by repeated restrained in water-treated and ethanol-treated rats could possibly occur due to an increase in sympathetic activity leading to enhanced excretion of these electrolytes.