The influence of the intravenous injection of single-dose diazepam on plasma potassium, sodium and chloride concentions was studied in 36 healthy patients undergoing minor surgical operations and this investigation was limited to the first 10 minutes after the intravenous injection of diazepam, 10mg. A significant decrease of plasma potassium concentration(-0.24~-0.25 mEq/1) was observed with diazepam at 5 and 10 minutes but the diazepam investigated in this study did not have a significant effect on the plasma sodium and chloride.