Doses of 1 to 2.3 mg./kg. of reserpine given intravenously to rabbits raised the plasma adrenaline. The noradrenaline concentrations were too near the threshold of the method to decide whether any alterations followed the injection of reserpine. Control experiments, in which blood samples were taken from rabbits but no drug was given, showed only a very slight rise in adrenaline concentration after the first bleeding.