Experimental aspiration of water soluble contrast agents was performed on rats via transoral endotracheal injection. Iopamidol, iohexol and diatrizoate were the contrast agents tested. One group of rats received normal saline as a control. Adjusted lung weights were measured at 2 and 24 hours post aspiration. Radiographs were taken at 2 and 24 hours post aspiration and scored for abnormal pulmonary air space density. Diatrizoate alone demonstrated an increase in adjusted lung weights. Diatrizoate, iopamidol and iohexol showed abnormal pulmonary air space disease on radiographs at 2 hours but not at 24 hours. Histopathologic examination of rat lungs following aspiration of all three contrasts showed pulmonary vascular congestion and perivascular edema. Iopamidol showed evidence of acute cellular inflammation. Iohexol provoked a pulmonary alveolar macrophage response.