Increased gallbladder (GB) pressure is probably a part of the pathogenesis of acute cholecystitis, and measurements of GB pressure might therefore be of interest. The aim of this study was to validate a microtip pressure transducer for intraluminal GB pressure measurements. In vitro precision and accuracy was within 0.2 mmHg, (SD) and 0.6 +/- 0.1 mmHg (mean +/- SD), respectively. Pressure rise rate was 24.8 +/- 5.5 mmHg s-1. Zero drift was in the range 0.3 +/- 0.4 to 0.8 +/- 0.9 mmHg (mean +/- SD). GB pressure was investigated in 16 patients with acute cholecystitis treated with percutaneous ultrasonically guided cholecystostomy. Basal intraluminal GB pressure was 8.9 mmHg (2.1-12.2 mmHg; n = 9, open cystic duct) and 1.8 and 5.8 mmHg (n = 2, closed cystic duct). There was no significant difference between two different measurements in the same patients (n = 5). The pressure was significantly influenced by respiration (n = 8) and the pressure seems to be higher in the sitting position than in the supine position (n = 5). Cystic duct opening pressure was 10.4, 11.2 and 16.8 mmHg (n = 3). Pressure-volume responses showed that the GB up to a certain volume could accommodate increases in intraluminal volume with only slight changes in intraluminal pressure (n = 4). Except for the zero drift, this piece of equipment seemed to fulfil the requirements of being able to measure pressure in the GB. In vivo measurements showed a good clinical reproducibility of the method, and also that respiration and patient posture influenced the pressure measurements. Further, a GB pressure-volume relationship was demonstrated, and the possibility of a cystic duct opening pressure was described.