Antibiotic therapy in recent years has become more intense and more frequent. Resistance acquisition by community and hospital strains is however also increasing. One of the methods to halt the increase in resistance may be shorter courses of antibiotics, if their clinical efficacy is not impaired. Shorter courses of antibiotic therapy have been very successful in typhoid fever: 3 days; in meningococcal meningitis: a single dose to 3 days' course; ventilator-associated pneumonia: 8 days; and possibly ICU-associated infections: 3-5 days. On the contrary, IV catheter-associated infections require full treatment courses (14 days). More studies are needed in various infectious entities with various agents to be able to better define the optimal duration of therapy.