Iodinated water-soluble compounds have been widely recommended as the most suitable contrast media for diagnosis of gastrointestinal perforations. However, the authors present 6 cases in which mucosal tears and transmural perforations of the upper gastrointestinal tract were either unrecognizable or inadequately shown during initial evaluation with methylglucamine diatrizoate. Re-examination with barium sulfate demonstrated the precise location and extent of the perforations. Reasons for the higher diagnostic yield of barium studies are explained on the basis of experimental and clinical observations.