PURPOSE: To describe the sonographic features of unusual macroscopic endosalpingiosis. MATERIALS AND METHODS: The clinical, pathologic and sonographic findings of eighteen patients which were histologically confirmed as endosalpingiosis were retrospectively reviewed. RESULTS: Nine of the eighteen cases did not have any abnormal sonographic findings. Their pathologic findings were single or multiple microcystic lesion with a diameter of less than one to two millimeters in the ovary, paratubal, peritoneum, and lymph nodes. The location of the other nine cases with abnormal sonographic findings were the ovary in three cases, paratubal in four cases, myometrium in one case, and ovary and myometrium in one case. The longest diameter of lesions ranged from 1.0 to 6.1 cm (mean 2.9 cm). They appeared as unilocular cyst in six cases and multilocular cyst in three cases with clear fluid content. Three cases had calcification. CONCLUSION: Endosalpingiosis was usually not detected on sonography due to its small, even microscopic size, however, it can present as an macroscopic lesions, showing an unilocular or multilocular cyst with calcification. Although these sonographic appearance of unusual endosalpingiosis may be nonspecific, the possibility of endosalpingiosis should be considered as a differential diagnosis.