OBJECTIVE The study was designed to observe the acute alterations between lower esophageal sphincter (LES) and intraabdominal pressure (IAP) in patients undergoing diagnostic laparoscopy. METHODS Eleven patients (7 Male), aged 49 fitting the criteria for manometric research and diagnostic laparoscopy were studied. To measure the IAP in sterile conditions a new device (IAP measurement system) was set. Pressures at basal (b), during intraabdominal CO2 insufflations (min, m2, m3) and at the end of laparoscopy (me), were recorded simultaneously. All results were given as the difference between two maneuvers (A). Paired sample t-test was used. RESULTS The results were as follows; at the time of maximum CO2 insufflations: p delta m1-b; 24.25 vs. 14.64 mmHg, during the stabile insufflations: p delta m2-m1; -2.88 vs. 2.99 mmHg, p delta m3-m2; -0.70 vs. -0.82 mmHg and after deflation of CO2; end of the laparoscopy; p delta m(e)-m3; -16.73 vs. -16.65 mmHg for LESP and IAP respectively. The response of the LESP and IAP were similar in all phases (p > 0.05). Also alterations of pressures according to gender or presence of cirrhosis were found to be similar. CONCLUSIONS LESP is changed synchronously in the presence of acute pressure changes in IAP. Gender or presence of cirrhosis does not affect the response of LES.