A prospective clinical study was conducted to evaluate whether or not any biochemical predictor of caustic ingestion and complicating esophageal injury exists. Children who were admitted to the hospital within 24 hours following caustic substance ingestion between 1994 and 2000 inclusive were evaluated. The ingested substance and complaints upon admission were noted. Groups were constructed according to the ingested substances such as household bleach (HB) (Group 1), acid (Group 2) or alkali ingestion (Group 3). Full biochemical analyses, chest X-ray and blood gas estimations were obtained and children were evaluated endoscopically. Seventy-eight children were studied. There were 19, 20 and 39 children in Groups 1, 2, and 3, respectively. There were no sex or age differences among groups (p>0.05). Esophagogastric injury was not encountered in Group 1. Second degree injury was present in 12 and 11 children in Group 2 and Group 3, respectively. Blood pH level was decreased in Group 1 (p=0.013), but not different in Groups 2 and 3 (p>0.05). pH did not differ in patients with or without esophageal injury (p>0.05). While serum uric acid values were significantly increased in children with esophageal burn (p=0.001), serum phosphorus and alkaline phosphatase levels were significantly decreased in children with esophageal injury (p=0.01 and p=0.019, respectively). Blood bicarbonate and serum potassium, chloride, urea nitrogen, creatinine, glutamic-oxaloacetic transaminase, glutamic-pyruvic transaminase, lactic dehydrogenase, calcium, glucose, protein, albumin and bilirubin levels did not differ between group (p>0.05), nor between patients with or without complicating esophageal injury (p>0.05). Low serum pH level is an indicator of HB ingestion. Routine endoscopy may not be necessary in children with normal blood pH values after ingestion. Although normal values of pH, uric acid, phosphorus and alkaline phosphatase levels do not rule out ingestion of an acid-or alkali-containing substance other than HB, increase in uric acid and decreases in phosphorus and alkaline phosphatase levels point to the presence of an esophageal injury.