In Switzerland 10 out of 1000 adults suffer from pneumonia each year. It is of note that mycoplasma, influenza virus and pneumococci are the most common causative agents of community-acquired pneumonia. For the latter macrolides are presently the antibiotics of choice. Pneumonias occurring in patients with immune disorders should be treated primarily with amoxicillin + clavulanic acid or with cephalosporins of the second generation, because infestation with germs like haemophilus influenzae and klebsiella pneumoniae have to be considered. If the empirically chosen therapy should fail, the therapeutic strategy should not be changed blindly. Differential diagnosis and appropriate investigations are necessary (other germ, other disease, complications?). Problems in treating patients with pneumonia are illustrated by three case examples.