In a double blind randomised study 3 different concentrations of iohexol for bowel opacification at CT of the abdomen were compared. Iohexol in a concentration of 4.5 mg I/ml, 6.75 mg I/ml and 9 mg I/ml was used. No significant differences between the 3 preparations of contrast media were found regarding the contrast effect, the distribution or patient tolerance. When using iohexol as a bowel contrast medium at CT the concentration of 4.5 mg I/ml is sufficient for bowel opacification.