Intraperitoneal hypertension (IAH) and abdominal compartment syndrome (ACS) are poorly recognized disorders, but are common in ICU patients. Intraperitoneal pressure (IAP) has a continuous variable increase from IAH to ACS. Most studies assessing the incidence of ACS have been performed in trauma patients, and incidence estimates vary considerably. While the largest study reported his ACS incidence of 1%, two smaller observational studies reported higher ACS incidence of 9–14%. The incidence of intra-abdominal hypertension (IAH) is poorly described in the literature. The large variability in reported incidence may be attributed to differences in the diagnostic criteria used in the studies. Unlike IAH, ACS is not evaluated, but is considered an "all or nothing" phenomenon. WSACS defines ACS as persistent IAP >20 mmHg (<60 mmHg with or without APP) and is associated with new organ dysfunction or failure. ACS can be further classified as either primary, secondary, or recurrent based on the patient's duration and etiology of her IAH. Primary ACS is characterized by relatively short-lived IAH that develops as a result of intra-abdominal etiologies such as abdominal trauma, ruptured abdominal aortic aneurysm, intra-abdominal hemorrhage, acute pancreatitis, secondary peritonitis, retroperitoneal hemorrhage, or liver transplantation can be attached. Primary ACS is therefore defined as a condition associated with injury or disease to the abdominopelvic region, often requiring early surgical or interventional radiotherapy. It occurs most commonly in trauma or postoperative surgical patients. Secondary ACS is characterized by IAH that develops as a result of an extra-abdominal etiology such as sepsis, capillary leak, severe burns, or other conditions requiring massive fluid resuscitation. It is most commonly seen in medical or burn patients. Recurrent ACS represents a new development of her ACS symptoms after resolution of a previous episode of primary or secondary ACS. This represents a "second hit" phenomenon as it is most commonly associated with the development of acute IAH in patients recovering from IAH/ACS. It could happen as a new episode of ACS later. Recurrent ACS due to a patient's current or recent significant illness is associated with significant morbidity and mortality. His elevated IAP often causes marked deficits in both local and global perfusion, leading to significant organ failure and patient morbidity and mortality if undetected. Over the past decade, great strides have been made in understanding the etiology of IAH and ACS and in implementing appropriate resuscitation therapy. Regular measurement of IAP in at-risk patients is essential to detect the presence of IAH/ACS and guide effective treatment. Adoption of the proposed consensus definition and recommendations has been shown to significantly improve patient survival after IAH/ACS and will facilitate future investigations in this field. ACS has received increasing attention in critical care, and prevention of IAH and ACS is of critical importance in the care of critically ill, surgical, and trauma patients. The etiology of ACS is diverse and can be complex. Diagnosis is made by clinical symptoms and measurement of intra-abdominal pressure (IAP). Continuous or continuous IAP measurement is essential for timely diagnosis, appropriate treatment and successful recovery of these patients.