PGA when administered subcutaneously into normal mice in a single injection produces after 24 hours an affective increase of the total weight and a decrease of the "alkaline" phosphatase of the kidneys. Normal values based on 54 mice are reported and compared with those obtained from 88 mice injected with graded doses of PGA (0.5mg/Kg to 500mg/Kg body weight. The "alkaline" phosphatase was determined by a slight modification of the colorimetric method of king & Armstrong using disodium phenylphosphate as a substrate. It is suggested that the retention and precipitation of PGA in the renal tubuli could be responsible for the increased weight and decreased phosphatase activity of the kidneys.