This chapter discusses the diagnosis, evaluation and management of abdominal compartment syndrome (ACS). The neurological presentation for the ACS includes increased intra-abdominal pressure (IAP) that is shown to decrease cerebral perfusion pressure by decreased cardiac output (CO) and hypotension, as well as via increased thoracic pressure with functional obstruction of cerebral venous outflow. The most efficient way to recognize and treat ACS is by recognizing and correcting predisposing factors before ACS occurs. In the closed abdomen, the gold standard approach to measure IAP uses a urinary bladder catheter (bladder pressures) with the patient in full supine position. Early recognition of risk factors and delaying definitive abdominal wall closure remains the best therapy for ACS. In cases in which the abdominal wall is already closed or the decompression is inadequate, timely intervention can be life-saving. ACS can occur even in the already decompressed abdomen.