During the winter of 1952-1953, a program was developed at the Philadelphia General Hospital to test the efficacy of several new drugs in the treatment of bacterial pneumonia. The program included 283 patients who were admitted to the medical wards with a diagnosis of pneumonia made in the receiving ward. An attempt was made to photofluorograph all these patients at weekly intervals until resolution of the pneumonia was complete or until the correct diagnosis became apparent. Pretreatment studies included, whenever possible, a 14 in. by 17 in. roentgenogram of the chest, complete blood cell count, sputum culture for pyogenic organisms, and blood culture. It was intended to investigate four regimens of therapy as follows: (1) 300,000 units of procaine penicillin administered intramuscularly twice a day, (2) carbomycin (Magnamycin), 500 mg. every six hours given orally, (3) erythromycin (Ilotycin), 300 mg. every six hours given orally, and (4) 500 mg. quantities