In spite of extreme and persistent susceptibility to antibiotics, specially benzylpenicillin, the pathology due to pneumococcus remains frequent and serious. From 14 cases of pneumococcal meningitis associated with pneumonia the authors have studied the relationship between these two localizations. They conclude that meningeal seeding appears most frequently secondarily and is probably latent at the beginning. Moreover they note that treatment of pneumonia by itself does not always prevent the occurence of the meningitis. Density of bacterial population, prolunged bacteremia, resistance of pneumococcus to phagocytic mechanisms and the delay of treatment might explain these findings. For those reasons the authors recommend the use of high doses of benzylpenicillin for the treatment of lately diagnosed bacterial pneumonia.