PURPOSE: Mucosal surface nodularity was defined as present at UGIS when multiple nodular defects larger than 5 mm were scattered in the gastric mucosa in an area greater than 5x5 cm. The purpose of this study was to determine the primary causes of this radiographic finding and to assess the incidence of gastric malignancy in these patients. MATERIALS AND METHODS: During a one-year period we prospectively collected among patients who underwent UGIS, data for 51 [aged 30-78(mean, 51) years] above who met the criteria of mucosal surface nodularity. Whether or not this was present was decided by two radiologists who in reaching a consensus excluded the possibility of erosive gastritis, indicated by central barium collection in the nodular defects. The primary causes of mucosal nodularity and associated gastric pathologies were determined by the histopathological results obtained from the specimens after surgery (n=18) or endoscopic biopsy (n=33). RESULTS: Pathological examinations revealed that the primary causes of the mucosal nodularity in these 51 patients were intestinal metaplasia in 28 (54.9%), MALT lymphoma in seven (13.7%), early gastric cancer in six (11.8%), chronic gastritis in five (9.8%), low grade dysplasia in four (7.8%), and gastritis cystica profunda in one (2%). Gastric malignancy was present either in or outside the area of mucosal nodularity in 34 (66.7%) of the 51 (27 carcinomas and 7 MALT lymphomas). No different patterns of mucosal surface nodularity were noted between the groups of each disease entity. CONCLUSION: Mucosal surface nodularity is observed at UGIS in various gastric pathologies. Because of the high incidence of gastric malignancy in these patients, close follow-up or gastrofiberscopic biopsy is mandatory.