Portal hypertensive gastropathy (PHG) and gastric antral vascular ectasia (GAVE) are unusual but important causes of gastrointestinal bleeding with characteristic endoscopic appearances and critically different therapies. However, overlapping features and poor endoscopic-histologic correlation make their distinction challenging. We sought to determine whether CD31, CD34 (vascular markers), and CD61 (platelet marker) could aid in their differentiation. Cases included 11 antral specimens with histologic diagnoses of GAVE, 11 histologically diagnosed as PHG, and biopsies of GAVE (15) or PHG (12) suspected on endoscopy but without histologic agreement. Controls consisted of endoscopically and histologically normal antrum. Image analysis of CD31 and CD34-stained sections was performed to determine mucosal microvessel density (MVD). CD61 revealed thrombi in 100% of histologically confirmed cases of GAVE and 60% of cases suspected of GAVE on endoscopy alone; control biopsies were negative. CD61 was also positive in 26% of cases originally signed out as PHG. Review of hematoxylin and eosin slides from these CD61-positive PHG cases showed other features allowing their correct reclassification as GAVE. MVD was significantly higher in GAVE than PHG. MVD in histologically confirmed PHG did not differ significantly from endoscopically suspected PHG. Review of hematoxylin and eosin slides from the latter showed active gastritis obscuring recognition of ectatic vessels. In conclusion, CD61 reliably differentiates GAVE from PHG. MVD analysis can also assist in their distinction. In PHG, the increased vascularity may be subtle in an inflammatory background; vascular markers may serve as adjunct markers for identifying the aberrant vessels.