Despite the consensus regarding spectrum and timing of antibiotic therapy, antimicrobial use varies across ICUs; indeed there are important variations in choice, dosing, method of administration, duration of antimicrobial therapy and de-escalation of empirical therapy. DetermInants of Antimicrobial use aNd de-escalAtion in critical care (DIANA study), is a multicenter, international, prospective, observational cohort study, aiming to describe the rate of de-escalation as well as the associated outcome and the empirical antibiotic therapy for infections at the intensive care unit.