Acinetobacter species have emerged as agents of serious nosocomial infections in critically ill patients. Only a few effective antibiotics are currently available for the treatment of this pathogen and, therefore, sulbactam is being considered as an alternative treatment option. The aims of this study were to i) reveal the population pharmacokinetics and ii) assess the probability of target attainment (PTA) of sulbactam in septic critically ill patients caused by Acinetobacter spp. infections.