Defining the optimal duration of antibiotic treatments is crucial to reduce toxicity and the emergence of resistance. Community acquired pneumonia can be treated in 5 days when the clinical response is rapidly favorable, as determined by simple clinical criterias. Acute cystitis can be treated by a 5-day course of nitrofurantoïne, or 3 days of trimethoprim-sulfaméthoxazole, saving the use of quinolones for complicated urinary tract infections or when the upper urinary tract is involved. Antibiotics are rarely needed for the treatment of sinusitis. When indicated, a 5-day course should suffice. There is no consensus for the duration of antibiotic treatment in skin infections. The benefit of inflammation biomarkers to diminish the duration of antibiotics has not yet been established for common infections.