A 12-year-old boy ingested a mercury battery from a watch as a part of an alleged poisoning attempt by an uncle. The battery apparently ruptured spontaneously in the child's stomach less than 36 hours after ingestion. At surgery one battery terminal was found embedded in gastric mucosa thought to be progressing toward gastric perforation. The unique complications of battery ingestion, such as gastrointestinal perforation and possible mercury poisoning, are reviewed. A strong recommendation for immediate endoscopic or surgical removal of ingested batteries is made. Parental education along with preventive measures by manufacturers such as package warnings, specific labeling of battery contents on each package, and "childproofing" of battery-containing products is stressed.