It has been the custom at the Children's Memorial Hospital to keep daily weight records of all children under 2 years of age, if not suffering with a contagious disease. Dr. Amberg called our attention to the fact that children who keep up their weight or gaining weight during a febrile disease, may begin to lose weight with the disappearance of the fever. In some cases, this happened abruptly, in others gradually. A closer survey of the cases showed that the loss was more likely to occur in cases of lobar pneumonia. From the years 1914 to 1919 we were able to collect fifty-two cases of pneumonia suitable for our study. In all but one of the twenty-eight cases ending with a crisis, there was some loss of weight coincident with the crisis. This loss was frequently quite marked. The cases are recorded in Table 1. They represent uncomplicated cases.