Endoscopic diagnosis of Helicobacter pylori infection, before biopsies and serological tests are performed, is possible through careful analysis of the network of superficial vessels in patients with gastritis. At standard endoscopy, a regular arrangement of the collecting venules (RAC) is visible as numerous minute red points in the corpus of the noninfected stomach, and is not visible in H. pylori gastritis. Magnifying endoscopy provides more precise information concerning the collecting venules, the network of capillaries surrounding the gastric pits, the swelling of the surface epithelium between pits, and the enlargement and destruction of the pits. The magnified appearance is classified as Z-0 (noninfected stomach) or as Z-1 to Z-3 for successive degrees of mucosal damage in the infected stomach. Histological controls confirm the reliability of the endoscopic classification. Magnifying endoscopy also proves helpful in the assessment of completeness of eradication of H. pylori.