The majority of community-acquired pneumonias are not hospitalized, have a good prognosis and a low mortality rate. In the nonimmunocompromised adult patient, pneumonias are caused by a broad array of microorganisms of which the so-called 'atypical' agents (mycoplasma, chlamydiae, viruses) are as frequently found as classical bacteria such as pneumococci and haemophilus. Generally, the mode of acquisition and the clinical picture will not allow to deduct the etiology with certainty, and the laboratory results are often nonconclusive (sputum examination) or delayed (serology). Empirical therapy should be initiated based on epidemiological grounds and on the characteristics of the patient. For patients without underlying conditions, immunosuppression or advanced age, a macrolide (erythromycin or a new macrolide) appears to constitute a good choice because of its broad spectrum of activity, comprising the classical bacterial agents of pneumonia, mycoplasma, chlamydiae, and legionella.