Chlamydia pneumoniae is a common cause of community-acquired pneumonia. At present there is no "gold'' standard for diagnosis and there is no easily accessible means of rapid diagnosis available. The best indication of acute C. pneumoniae infection is a fourfold rise in antibody titer, accompanying a positive polymerase chain reaction or culture. C. pneumoniae is usually associated with nonsevere clinical manifestations but the features will vary depending upon the occurrence as primary or reinfection syndrome, the presence of co-pathogens, or the existence of co-morbid conditions. C. pneumoniae has been described as a cause of severe disease requiring intensive care unit admission. Recommendations for therapy of C. pneumoniae pneumonia include macrolides, tetracyclines, or the new fluoroquinolones.