In a double-blind randomized study 3 different preparations of oral contrast media for bowel opacification at CT of the abdomen have been compared. Plain aqueous solutions of amidotrizoate (9 mg I/ml) and iohexol (9 mg I/ml) were used as well as a preparation of iohexol (9 mg I/ml) to which a viscosity-increasing agent had been added. The distribution of the contrast media in the intestine, transit time and patient tolerance were evaluated. No significant differences were found regarding the distribution between the 3 preparations of contrast media, while there was a tendency for the transit time to be increased when the viscous preparation of iohexol was used. The aqueous solution of iohexol had the best taste, while the viscous preparation was markedly more difficult to drink. Aqueous solutions of iohexol and amidotrizoate were equal for bowel opacification and the addition of the viscosity-increasing agent did not improve the distribution of the contrast medium in the intestine.