The Infectious Diseases Society of America (IDSA) has published guidelines for the treatment of community-acquired pneumonia (CAP). Although Streptococcus pneumoniae remains the most common etiologic agent, Chlamydia pneumoniae and Legionella pneumophila are also important causes. For all suspected CAP patients, particularly those requiring hospitalization, chest radiographs are strongly recommended to confirm the diagnosis. The IDSA guidelines, in contrast to those published by the American Thoracic Society, emphasize the use of sputum Gram's stain and culture in all patients, whenever possible, to establish etiology. This information can be used not only to guide therapy but also to track trends in the etiologic pathogens for CAP and their antibiotic susceptibility. In light of the better outcomes with the earliest possible interventions, the IDSA recommends initial empiric antimicrobial therapy until laboratory results can be obtained to guide more specific therapy. Macrolides, doxycycline, and fluoroquinolones are suggested for primary empiric therapy, since each has activity against common bacterial pathogens and atypical agents. Detailed antibiotic recommendations are made for various pathogens. For inpatients, attempts should be made to cover Legionella and other common pathogenic bacteria. Alternative antibiotics are recommended for patients with structural diseases of the lung, penicillin allergy, or suspected aspiration pneumonia. Switch to an appropriate oral antibiotic is recommended as soon as the patient's condition is stable and he or she can tolerate oral therapy, often within 72 h.