Gastrografin® and Amipaque® with identical iodine content and flavoring were orally administered in 100 ml doses to 10 healthy volunteers in a double-blind crossover study. The nonionic Amipaque has only about one third of the osmolality of Gastrografin, and draws less fluid into the bowel lumen. Consequently there is less dilution with Amipaque, and a higher contrast density in the ileocecal region can be observed. Unlike the highly hypertonic Gastrografin, Amipaque causes less changes in hematocrit, and has only a very mild cathartic effect. No more than 0.4% of the iodine in Amipaque was excreted in the urine during one day, and no more than 0.8% during three days. This was less than the excretion found after ingestion of Gastrografin. Non-ionic media are recommended when there is an indication for use of water-soluble contrast media in the gastrointestinal tract.