Upper gastrointestinal inflammatory processes are exceedingly common and have a wide spectrum of causes and manifestations. The broad category of acid-peptic disease incorporates the most common and important conditions. Concepts of pathophysiology of gastritis and duodenitis and their relationship to ulcers and neoplasm continue to evolve. The role of infection, especially H. pylori, remains under intense investigation. The spectrum of gastroduodenal inflammation in the immunocompromised host continues to expand and becomes increasingly important. A variety of granulomatous processes, both infectious and idiopathic, involve the upper gastrointestinal tract in overlapping patterns. Although investigation of ulcers and syphilis occupied the attention of the earliest gastrointestinal radiologists, related problems continue to challenge today's radiologic imagers, clinicians, and investigators.