Prostaglandin E2 formation and content has been measured in the stomach and small intestine of rats after acute and chronic ethanol ingestion. Chronic ethanol administration for 6 and 12 weeks inhibits PGE2 synthesis and reduces PGE2 content (12 weeks) in all parts of the upper gastrointestinal tract, while after ethanol ingestion up to 1 week PGE2 synthesis is decreased only in the stomach.