Broadly speaking, the potassium salts increase the amount of urine formed by the kidneys, but the result of the experiments on such a diuretic action of these substances varies with either quantities or methods for its application, or animals for experiments. Hence the opinion regards this diuresis is at present divided. Having ascertained the effect of the potassium salts on the amount of urine in bufo japonicus and rabbit, the author injected a solution of potassium acetate into the vein of non anaesthetised rabbit three times a day or gave it through the stomach and observed the increase of urineflow as well as the condition of blood (a specific gravity, the number of red corpuscles, the osmotic pressure). The results can be shown as follows. 1. When a hypotonic solution of potassium salt, such as potassium nitrate or acetate is injected into the circulation (or into the perfusing fluid) of a anaesthetised frog, distinctly the flow of urine at first decreases, again it may increase slightly. 2. In non-anaesthetised rabbit, a frequent injection or oral application of a little quantity of hyper- as well as hypotonic solutions of these salts, brings about more or less in many cases the increase of the urineflow. 3. Under the same effect of these substances, it takes place not only a diuresis but a condition of a slight hydraemie plethora. Further the osmotic pressure of the blood falls, too. 4. Whatever the application may be, the potassium acetate usualy leads to a hydraemie and to an increased flow of urine. But both does not occur invariably always to the same extent. 5. It is not to be considered, that the condition of hydraemie plethora may be the only cause of the diuresis owing to potassium salts, but such a hydraemie takes, in all probability, a active share in this form of diuresis. 6. It may be shown that the process of vasoconstriction resulting of potassium salts acts, in the other hand, to disturb the diureses of these substances.