It has been established that specific liver poisons (chloroform, phosphorus) which cause histological changes in the liver cells, decrease the liver excretion of phenoltetrachlorphthalein. Also vascular disturbances (Eck fistula, passive congestion) with or without histological evidence may cause a fall in the output of phthalein through the liver. Sufficient evidence has been brought forward to show that the phenoltetrachlorphthalein excretion is a valuable index concerning the functional capacity of the liver. Ether anesthesia for a period of two hours usually causes a depression in the phthalein curve during the twenty-four hours following the anesthesia. Paraldehyde in doses sufficient to give anesthesia and stupor for a few hours will give adefinite fall in phthalein excretion. Chloral and urethane usually cause a decrease in phthalein output when given in considerable amounts. Alcohol causes a drop in the phthalein curve when given in large doses sufficient to cause stupor for a few hours. The drop in phenoltetrachlorphthalein excretion is demonstrated in the twenty-four hours following administration of the drug. A drop in the phthalein curve to two-thirds or one-half of normal indicates a definite liver injury and temporary impairment of function.