Concentrated lye rapidly produces liquefaction necrosis, which can completely dissolve organs of the upper gastrointestinal tract, damaging adjacent structures including, in rare instances, even the transverse colon. Patients so afflicted will survive only if the injury is promptly detected and treated by radical surgical extirpation of all necrotic tissue. Symptoms are unreliable, and definitive diagnosis requires endoscopic evaluation. For years endoscopists were warned to stop at the first site of injury to avoid perforation of the damaged esophagus, but fiberoptic instruments now allow panendoscopy to be safely performed in almost all cases. Endoscopy alone, however, cannot detect extraluminal injury. If there is visual evidence of injury to the duodenum, computed tomography should be routine to search for injury to adjacent structures. Even in the absence of duodenal injury, computed tomography may prove valuable in assessing and managing patients with extensive damage to the esophagus or stomach. In cases of mediastinal or intraabdominal visceral necrosis, steroid therapy, by depressing the patient's ability to mount an inflammatory response, might worsen the injury and lead to life-threatening sepsis. The use of corticosteroids to treat patients following ingestion of caustic substances should therefore be abandoned as both ineffective and potentially dangerous.