Sucralfate is an effective agent in reducing the incidence of upper GI tract (UGIT) stress bleeding and nosocomial pneumonia in critically ill patients. Many of these patients are not intubated and are at increased risk for aspiration of large volumes of UGIT contents containing sucralfate. The effects of aspirated sucralfate are unknown. To investigate this, large-volume aspiration (2 ml/kg) was simulated in freshly tracheostomized rats (n = 6, all experimental groups) using normal saline, particulate antacid, and sucralfate adjusted to pH 3.6 and 5.0. Four hours after aspiration, the rats were killed and their lungs were formalin-fixed. Significant increases in lung inflammation were seen by light microscopy in all experimental groups at pH 3.6. Antacid aspirated at pH 5.0 induced significant increases in airway as well as parenchymal inflammation. At pH 3.6, the antacid aspiration led to significant increases in lung edema and hemorrhage. Sucralfate aspiration produced significant increases in pulmonary hemorrhage at pH 5.0. Our microscopic findings are consistent with the acute pulmonary histopathologic changes known to occur after large-volume aspiration of particulate materials, including antacids. Additionally, we show that large-volume aspiration of sucralfate produced significant acute pneumonitis, including pulmonary hemorrhage. In view of the proven usefulness of sucralfate, further investigations are indicated to evaluate these experimental findings before extrapolating to critically ill patients.