General Major role for H. pylori,spiral urease-producing organism that colonizes gastric antral mucosa in up to 100% of persons with DU and 80% with GU. Also found in normals (increasing prevalence with age) and those of low socioeconomic status. Invariably associated with histologic evidence of active chronic gastritis, which over years can lead to atrophic gastritis and gastric cancer. Other major cause of ulcers is NSAIDs (those not due to H. pylori).