OBJECTIVE To prospectively evaluate intraluminal pressure changes in the colon of children undergoing conventional hydrostatic (barium and water-soluble contrast material) and air contrast barium enema studies. METHODS Dynamic intracolonic pressure was measured in 26 children undergoing hydrostatic barium (23% wt/vol) enema studies, air contrast barium enema studies, or water-soluble contrast material enema examinations. Measurements were obtained with a measuring device capable of recording rapid changes in pressure. Pressure measurements were obtained with the contrast reservoir system open (contrast material was free to run through the tubing into the patient's colon) and closed (tube was clamped). RESULTS The colonic pressures during the filling phase with liquid contrast material were equal to those elsewhere at the same level with the hydrostatic system. Mean pressure ranged from 30 to 50 mm Hg with peaks of more than 100 mm Hg during Valsalva maneuvers. During air contrast barium enema studies, sharp pressure increases and rapid swings in the intracolonic pressure occurred during and after manual insufflation of air. CONCLUSIONS During conventional hydrostatic barium enema studies, intracolonic pressures remain low. During air insufflation, there were intermittent high, sharp pressure peaks.