An intra-abdominal hypertension (IAH) defined as a pathological increase in intra-abdominal pressure (IAP) is commonly found on ICU admission or during the ICU stay. Several studies confirmed that an IAH is an independent predictor for mortality of critically ill patients. The abdominal compartment syndrome (ACS) which is defined as a sustained IAP>20 mmHg (with or without an abdominal perfusion pressure [APP]<60mmHg) that is associated with new organ dysfunction or failure has a mortality of up to 60%. In general, an IAH may be induced by several intra-abdominal as well as extra-abdominal conditions. Reduced abdominal wall compliance, intra-abdominal pathologies (either of the peritoneal space or parenchymateous organs) may lead to an IAH. Most commonly, intra-abdominal infections and/or sepsis and severe trauma or burns are predisposing for an IAH. An early sign may be a decrease in urinary output. The effects of an increased IAP on cardiovascular function are well recognized and include negative effects on preload, afterload and contractility. However, all other compartments of the body may be affected by an IAH. Thus, by an increase of the respective compartment pressure, e.g. intracranial pressure, a poly-compartment syndrome may result. Adequate prevention, a forward-looking strategy, and objective techniques for measurement of IAP are required to avoid or early detect an IAH or ACS. Finally, an immediate and consequent interdisciplinary management using conservative, interventional and operative options are necessary to solve an IAH or ACS.