To assess the clinical value of endoscopic ultrasonography (EUS) in carcinoid tumors of the rectum, we studied endoscopic and EUS findings in five patients whose tumors were relatively small in size. Endoscopy revealed sessile or semi-pedunculated smooth elevations, with mucosa of normal appearance. The elevations ranged from 5 to 15 mm in diameter, and were yellowish to white in color. EUS failed to demonstrate a small tumor in two patients whereas in the remaining three patients, a homogeneously hypoechoic mass, which was restricted to the submucosal layer, was detected. All patients were treated by endoscopic excision or local resection of the tumor, which resulted in complete removal of the tumor. We believe that even though EUS is not efficacious in cases of very small carcinoid tumors of the rectum, it can provide clinically important information in choosing therapy.