Aspiration is a serious complication of oral contrast media (CM). The authors investigated the effects of iotrolan, iopamidol, and diatrizoate in rats' lungs. To quantify the lung damage induced by CM, pulmonary water and hemoglobin contents were determined. Arterial blood-gas exchange (pH, PCO2, and PO2) also was determined as an indicator of respiratory function. Iotrolan, iopamidol, or sodium/meglumine diatrizoate with a concentration of 300 mg I/mL was administered intrabronchially at a dose of 1 mL/kg. Physiologic saline was administered to the control group. Ten minutes after administration, arterial blood was collected and the lung was removed. Diatrizoate and iopamidol increased pulmonary water and hemoglobin contents and decreased blood PO2. The effect of iotrolan on these parameters was slight and no significant differences were observed between the iotrolan and saline groups. These results suggest that iotrolan is a preferable CM for gastrointestinal examination in the case of suspected aspiration.