This study was designed to establish if clinical examination can accurately predict intraabdominal pressure (IAP). Between August 1998 and March 2000 a prospective blinded observational study of postoperative intensive care unit patients was undertaken at a major trauma center. IAP was measured using an intravesicular technique and compared with clinical evaluation. An IAP of at least 18 mmHg was considered elevated. The sensitivity, specificity, positive predicative value (ppv), negative predictive value (npv), kappa score, and reliability analysis were calculated. A total of 110 patients provided 150 estimates of IAP, which was elevated in 21%. The kappa score was 0.37; sensitivity, 60.9%; specificity, 80.5%; ppv, 45.2%; npv, 88.6%. The mean difference in IAP values between intravesicular readings and clinical estimates was -1.0 +/- 4.1. Prediction of IAP using clinical examination is not accurate enough to replace intravesicular IAP measurements.