Intra-abdominal hypertension has a prevalence of at least 50% in the critically ill population and has been identified as an independent risk factor for death. Yet, many of the members of the critical care team do not assess for intra-abdominal hypertension and are unaware of the consequences of untreated intra-abdominal hypertension. These consequences can be abdominal compartment syndrome, multisystem organ failure, and death. This article provides an overview of the pathophysiology of intra-abdominal hypertension and abdominal compartment syndrome. In addition, the evidence-based definitions, guidelines, and recommendations of the World Society of the Abdominal Compartment Syndrome are presented.