This bacteriological study of 201 autopsy reports was designed to throw some light on what is being accomplished, with particular reference to pneumonia, by the widespread use of antibiotics as currently practiced. For purposes of comparison, we had the past records in our own Department of Pathology, and the reports of similar studies performed before the introduction of these relatively new therapeutic agents. Certain obvious conclusions were immediately apparent: “Old-fashioned” lobar pneumonia as a cause of death has almost entirely disappeared, and the organisms that were formerly considered of greatest significance in terminal pneumonia, all of which are uniformly sensitive to antibiotics and do not tend to acquire resistance, have likewise withdrawn from the scene. These three are the pneumococcus, the group A hemolytic streptococcus and H. influenzae. Their place has been taken by the staphylococcus, which has become relatively more prominent than formerly, and several gram-negative bacilli. As the single bacterial incitant of pneumonia contributory to the death of the patient, staphylococci were incriminated nearly three times as often as all the gram-negative bacilli combined. However, when one considers total numbers (seventeen of 201), one does not get the impression of an epidemic out of control. The finding of staphylococci and pneumonia at autopsy appeared to be uninfluenced by antibiotic treatment prior to death. Most of the strains recovered were more or less resistant to antibiotics, but a review of all our cases yielded not a single instance in which a fatal staphylococcal pneumonia appeared to have been induced by needless antibiotic therapy in a patient who might otherwise have recovered. Undoubtedly terminal staphylococcal pneumonia is a prominent feature of the clinical scene today, but the finding of staphylococci in nearly one-third of normal lungs (more often than not in abundant growth) suggests that this organism is a less specialized pulmonary pathogen than the pneumococcus. Pyocyaneus was next in importance to staphylococcus in relation to terminal pneumonia, and was found almost exclusively in patients receiving antibiotics. It was considered only twice, however, as the sole bacterial cause of pneumonia contributory to the death of the patient. Thus the organism would seem to have limited potentialities as a pulmonary pathogen. Pyocyaneus pneumonia appears to be a product of the antibiotic era, yet we did not find a single fatal case of this disease in which antibiotics had been needlessly employed in a patient who might otherwise have survived. Klebsiella-aerogenes appeared to have about the same significance in terminal pneumonia as pyocyaneus. Infection with this organism, however, seemed unrelated to antibiotics. Terminal pneumonias associated with proteus or E. coli occurred more commonly in patients not receiving antibiotics. We have also reported the bacteriological and histologic findings in six major disease groups which accounted for 145 of our 201 cases. As might be expected, the incidence of pneumonia and of positive bacteriological cultures is extremely low in patients dying of coronary insufficiency. The most noteworthy finding in the other five disease groups, all of them chronic, was that the patient with cholemia appeared to be an excellent culture medium but with a limited capacity for inflammatory response. There were two cases of pseudomembranous enterocolitis in our series. Both these patients had received “prophylactic” antibiotics during the postoperative period, and we have assumed that death in each case was the result of unnecessary use of antibiotics. These are the only two instances of such an event in a patient who might otherwise have survived. As there is obviously no way of determining in a series of patients who have died how often antibiotics save life, the vexed question of the advisability of their widespread use cannot be answered from our data. We may simply restate our opinion that antibiotics have modified the pattern rather than the incidence of terminal pneumonia. Finally, we should like to give a word of comfort to the ardent therapeutist who wishes to fight the longest possible rear-guard action in a hopeless cause. We have considered in some detail six organisms which seem to have taken over the role of terminal pulmonary pathogens. In twenty-six cases pneumonia contributory to the death of the patient appeared to be due to a single one of these bacteria, and in only five instances was the patient receiving an antibiotic to which that particular organism was sensitive. One concludes that the right antibiotics still have efficacy even at the end stage of chronic disease.