We have previously reported the effectiveness of endoscopic ultrasonography (EUS) for the differential diagnosis of pedunculated polypoid lesions of the gallbladder, based on retrospective studies using resected specimens. We proposed the following diagnostic criteria for EUS findings: when the contour of a lesion is nodular or smooth, the lesion is diagnosed as a neoplasm, and when a lesion has a granular contour, it is diagnosed as a nonneoplasm. The present study was designed to verify the clinical utility of our EUS ctiteria prospectively. Methods. Forty-six consecutive patients with pedunculated polypoid lesions of the gallbladder 10 mm or greater in size diagnosed as nonneoplasms at the initial EUS, all of whom underwent follow-up examinations, were enrolled in this study. The occurrence of changes in these lesions during the observation period was examined. Results. No evident changes in lesions were observed in 43 of the 46 patients. Spontaneous self-detachment of lesions was recognized during the observation period in the other 3 patients. Conclusions. EUS is useful for determining treatment indications for pedunculated polypoid lesions of the gallbladder, even when the lesions are large, and contributes to avoiding unnecessary surgery.