Many patients with pneumonia, especially those who are more severely ill, have their first medical contact in the emergency department. Pneumonia is usually diagnosed with appropriate signs and symptoms, although these can be lacking in the very young or the old. Gram stain and culture are seldom useful. The choice of appropriate antibiotic is usually determined by degree of illness and microbiological epidemiology. The most important decision made in the emergency department is whether to admit the patient with pneumonia to hospital; this decision can be aided by the use of clinical predictive rules. Initial treatment of pneumonia includes supportive care as needed (oxygen, intubation and bronchodilators) and an empirically chosen antibiotic. Appropriate choices include macrolides and azalides for low risk out-patients, and either a combination cephalosporin and macrolide or an extended spectrum fluoroquinolone in anticipation of drug-resistant Streptococcus pneumoniae for high risk out-patients and in-patients.