Although the normal adrenal gland is seldom detected, ultrasonography can detect adrenal tumors more than 1 to 2 cm in diameter. For imaging the adrenal gland, CT and MRI are superior to ultrasonography; however, ultrasonography is the better choice for the initial examination of the adrenal glands of children and pregnant women. Ultrasonography usually shows a homogeneous hypoechoic mass in adenomas, and a heterogeneous mass in pheochromocytomas and carcinomas. Adenomas, however, are difficult to differentiate from metastatic and other adrenal tumors, especially when the tumors are small. In myelolipomas, ultrasonography depicts the characteristic hyperechoic mass. A combination of both imaging methods is necessary for a detailed diagnosis of an adrenal tumor. Ultrasonography can be used to guide the needle when puncturing an adrenal tumor and to diagnose the tumor intraoperatively in laparoscopic adrenal surgery. Because ultrasonography is always used in routine physical examinations and is the imaging modality of choice for children and pregnant women, knowledge of the ultrasonography of the adrenal gland is essential. Also, because the incidence of incidentaloma, incidentally discovered adrenal tumor, will increase, ultrasonography is likely to become important in following up the clinical course of incidentalomas.