OBJECTIVE: To investigate whether the compartment pressure of the rectus sheath (CPRS) reflects the intra-abdominal pressure (IAP) under various conditions of intra-abdominal hypertension (IAH). DESIGN AND SETTING: Prospective experimental study with in vivo pressure measurements at the Institute for Clinical and Experimental Surgery, University of Saarland. ANIMALS: Sprague-Dawley rats. INTERVENTIONS: Stepwise increase and decrease in IAP with continuous measurement of the correspondent CPRS. MEASUREMENTS AND RESULTS: Physiological IAP (2 mmHg) and CPRS (6 mmHg) showed a statistically significant difference. Stepwise elevation in IAP was associated with a simultaneous increase in CPRS. Accordingly, stepwise decompression of IAP resulted in a stepwise decrease in CPRS. Under both conditions Bland-Altman analysis comparing IAP to correspondent CPRS showed a very good agreement for IAP at or above 12 mmHg. In addition, closure of the overlaying subcutaneous tissue and skin did not affect CPRS or its correlation with IAP. CONCLUSIONS: CPRS accurately reflects IAP for IAP of 12 mmHg or higher. Thus CPRS measurements may represent a novel approach for diagnosis and monitoring of IAH.