Acute infections of the deep lung contracted outside a hospital environment are termed community-acquired or home-based pneumonia. This disease is still the sixth commonest cause of death in industrialized countries. The clinical picture varies from mild involvement to cases requiring prompt therapeutic interventions and hospitalization. Identification of the aetiological agent is often impossible, and in > 50% of patients antibacterial treatment is chosen on empirical grounds alone. Streptococcus pneumoniae, Haemophilus influenzae and Mycoplasma pneumoniae are still the most commonly occurring pathogens, but aetiology varies according to age group. Presenting symptoms may differ, and distinction between typical and atypical pneumonia is complex. The degree of severity of disease must be assessed in order to determine whether outpatient treatment is sufficient or whether hospitalization is required. Invasive and noninvasive techniques may be employed to reach an aetiological diagnosis. Most cases of community-acquired pneumonia may be effectively treated at home. However, it is important to recognize high-risk conditions that require immediate hospitalization. Choice of treatment is generally based on empirical criteria, adapting antibiotic selection to the clinical characteristics of the disease and individual patient conditions.