Objective: The diagnoses of patients with duodenal protruding lesions are difficult when using conventional ex- aminations such as computed tomography (CT) and conventional endoscope etc. Thus, we investigated the clinical value of endoscopic ultrasonography (EUS) with miniature ultrasonic probes on the diagnosis and treatment of duodenal protruding lesions. Methods: Patients with duodenal protruding lesions who were indicated for EUS were examined by EUS with 12~15 MHz miniature ultrasonic probes and double-cavity electronic endoscope. According to diagnosis of EUS, those patients were indicated for biopsy and treatment received biopsy, endoscopic resection or surgical excision. The postoperative histological results were compared with the preoperative diagnosis of EUS. Those patients without endoscopic resection or surgical excision were peri- odically followed up with EUS. Results: A total of 169 patients with duodenal protruding lesions were examined by EUS, of which 40 were diagnosed with cysts, 36 with inflammatory protruding or polyp, 25 with Brunner’s gland adenoma, 19 with ectopic pancreas, 17 with gastrointestinal stromal tumor, 12 with extrinsic compression, 12 with minor papilla, 6 with lipoma, 1 with adenocarcinoma and 1 with lymphoma. After EUS examinations, 75 patients received biopsy, endoscopic resection or surgical excision respectively. The postoperative histological results of 70 patients were completely consistent with the preoperative diagnosis of EUS, with 93.33% diagnostic accuracy. The results of follow-up with EUS indicated that duodenal cyst, Brunner’s gland adenoma, ectopic pancreas, gastrointestinal stromal tumor and lipoma remained unchanged within 1~3 years. No related complications occurred among all patients that received EUS examinations. Conclusion: EUS is an effective and reliable diag- nostic method for duodenal protruding lesions. Objective: The diagnoses of patients with duodenal protruding lesions are difficult when using conventional ex- aminations such as computed tomography (CT) and conventional endoscope etc. Thus, we investigated the clinical value of endoscopic ultrasonography (EUS) with miniature ultrasonic probes on the diagnosis and treatment of duodenal protruding lesions. Methods: Patients with duodenal protruding lesions who were indicated for EUS were examined by EUS with 12-15 MHz miniature ultrasonic probes and double-cavity electronic endoscope. According to diagnosis of EUS, those patients were indicated for biopsy and treatment received biopsy, endoscopic resection or surgical excision. The postoperative histological results were compared with the preoperative diagnosis of EUS. Those patients without endoscopic resection or surgical excision were peri- odically followed up with EUS. Results: A total of 169 patients with duodenal protruding lesions were examined by EUS, of which 40 were diagno sed with cysts, 36 with inflammatory projection or polyp, 25 with Brunner’s gland adenoma, 19 with ectopic pancreas, 17 with gastrointestinal stromal tumor, 12 with extrinsic compression, 12 with minor papilla, 6 with lipoma, 1 with adenocarcinoma and 1 with lymphoma. After EUS examinations, 75 patients received biopsy, endoscopic resection or surgical excision respectively. The postoperative histological results of 70 patients were completely consistent with the preoperative diagnosis of EUS, with 93.33% diagnostic accuracy. The results of follow-up with EUS indicate that duodenal cyst, Brunner’s gland adenoma, ectopic pancreas, gastrointestinal stromal tumor and lipoma remained unchanged within 1 ~ 3 years. No related disorders occurred among all patients that received EUS examinations. Conclusion: EUS is an effective and reliable diag- nostic method for duodenal protruding lesions .