The aim of the present project was to evaluate the prognosis of small and asymptomatic cysts of the pancreas which were diagnosed as being nonneoplastic by endoscopic ultrasonography. Eighty-two patients with such cysts had been subjected to ultrasonographic examination every 6 months. Results of follow-up for 3 or more years were obtained in 31 patients. The cysts disappeared in 4 patients and enlarged in 1 patient. The others did not show any morphological changes. The enlarged cyst turned out to be a retention cyst after surgical resection. Our endoscopic ultrasonographic criteria were effective for small nonneoplastic cysts of the pancreas, and most of these cysts appeared to be nonprogressive.