Bacterial pneumonia remains a serious infectious disease even in the modern era of antibiotics and still causes significant morbidity and mortality. Because of the large number of organisms that may cause pulmonary disease, the inexactness of commonly used diagnostic techniques, and the serious consequences of untreated disease, empiric therapy has become accepted practice. Empiric therapy should be designed for treatment of the most likely etiologic organisms while minimizing the potential adverse effects of “shotgun” therapy: drug toxicity, superinfection, and excessive cost. The recognition of common pneumonia syndromes helps narrow the spectrum of possible etiologic agents and consequently aids in the design of rational empiric antibiotic therapy.