Acute bronchitis is usually a viral infection which, unless there is a special disposition, does not require antibiotic therapy, For the initial oral chemotherapy of bacterial infections of the lower respiratory tract (chronic bronchitis, pneumonia) the effective and well tolerated cephalosporins, macrolides and amoxicillin plus beta-lactamase-inhibitor are recommended. In complicated cases with severe underlying disease, longer history or frequent exacerbations, quinolones should be given if Gramnegative infections are suspected or if initial therapy with other substances has failed, If Legionella, Mycoplasma or Chlamydia spp., so-called 'atypical' pathogens, are involved, macrolide antibiotics are the therapy of first choice. Special attention should be given to the increase in resistance against cotrimoxazole (trimethoprimsulfamethoxazole) and tetracyclines. In hospitals where primary pneumonias are treated preferentially by intravenous medication, therapy should be switched to oral antibiotics as soon as feasible (follow-up therapy). For severely ill patients with secondary pneumonia and underlying disease, second generation cephalosporins with aminoglycosides, or monotherapy with third generation cephalosporins are recommended. In very severe, high-risk cases, third generation cephalosporins, combinations with high-dosage quinolones or ureidopenicillins plus P-lactamase-inhibitors are suitable. Future development in the antibiotic treatment of respiratory infections will follow the current trend of lower dosages, with the clear objective of shortening treatment periods and achieving earlier discharge from hospital.