Background/Aims: Intra-abdominal hypertension (IAH) is being increasingly reported in patients with severe acute pancreatitis (SAP) with worsened outcomes. The present study was undertaken to evaluate intra-abdominal pressure (IAP) as a marker of severity in the entire spectrum of acute pancreatitis and to ascertain the relationship between IAP and development of complications in patients with SAP. Methods: IAP was measured via the transvesical route by measurements performed at admission, once after control-ling pain and then every 4 hours. Data were collected on the length of the hospital stay, the development of systemic inflammatory response syndrome (SIRS), multiorgan failure, the extent of necrosis, the presence of infection, pleural ef-fusion, and mortality. Results: In total, 40 patients were en-rolled and followed up for 30 days. The development of IAH was exclusively associated with SAP with an APACHE II score ≥8 and/or persistent SIRS, identifying all patients who were going to develop abdominal compartment syndrome (ACS). The presence of ACS was associated with a significantly in-creased extent of pancreatic necrosis, multiple organ failure, and mortality. The mean admission IAP value did not differ significantly from the value obtained after pain control or the maximum IAP measured in the first 5 days. Conclusions: IAH is reliable marker of severe disease, and patients who mani-fest organ failure, persistent SIRS, or an Acute Physiology and Chronic health Evaluation II score ≥8 should be offered IAP surveillance. Severe pancreatitis is not a homogenous entity. (Gut Liver 2013;7:731-738)