Gastric antral vascular ectasia was endoscopically diagnosed in seven patients. Pathologic characteristics of this entity were defined retrospectively, by studying endoscopic pinch biopsy slides from these seven patients and antrectomy specimens from five patients. A scoring system was developed, and the seven patients were compared prospectively with various control groups. Abnormalities of mucosal vessels (fibrin thrombi and/or ectasia) consistently distinguished patients from control antrectomies, normal biopsies, acute gastritis biopsies and atrophic gastritis biopsies (P = 0.02, all comparisons). Spindle cell proliferation into mucosa also was characteristic of gastric antral vascular ectasia, distinguishing this disease from normals, acute gastritis, and atrophic gastritis (P less than or equal to 0.039, each comparison). The presence of abnormal mucosal vessels (fibrin thrombi and/or ectasia) and spindle cell proliferation was similar in patient antrectomies compared to patient endoscopic biopsies. Therefore, we conclude that endoscopic biopsies can reliably diagnose gastric antral vascular ectasia, a vascular disorder characterized by abnormal mucosal vessels and spindle cell proliferation.