For any syndrome or disease process, uniform definitions are essential to facilitate effective clinical communication as well as evaluation of the scientific literature and standardization of research. The following consensus definitions for intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) have been proposed by the World Society of the Abdominal Compartment Syndrome and are now widely accepted around the world. The use of these definitions, and their subsequent revisions as new evidence becomes published, will further improve communication and future research in this area. This review briefly addresses the present definitions as well as the pathophysiological effects of IAH/ACS on end-organ function.