1. It has been found that the amount of glycuronic acid excreted in the urine, estimated by Tollens's furfurol distillation method, is increased during the febrile period of almost all cases of lobar pneumonia in man. Patients weighing from fifty-five to seventy kilograms excrete during the febrile period 0.8 to 1.3 grams of glycuronic acid in twenty-four hours, while the output of a normal individual of the same weight, age, and under similar conditions would not exceed 0.4 to 0.6 of a gram. 2. This increased output is not dependent on outside factors; it is attributable to pathological changes of the organism itself during the disease. 3. Similar observations have been made in postpneumonic empyema and bronchopneumonia. 4. Fasting rabbits, with general pneumococcus infection, have also shown a marked increase in the output of glycuronic acid during the pathological process. Whether the conjugated substances with the glycuronic acid in the cases studied have the same origin and are qualitatively the same as under normal conditions, or whether we are dealing with different compounds, has not yet been determined.