Ultrasound (US) is a simple and noninvasive modality, but it is susceptible to interference from gas echoes, and the ability of US depends on the level of diagnostic skill of the sonographer. It is also important that the sonographer know about the characteristics of artifacts and how to remove their influence. Gallbladder lesions are arbitrarily classified into three types including pedunculated, broad based and wall-thickened (flat) types. This classification is very important not only to make a differential diagnosis but also to evaluate the depth of cancer invasion; the pedunculated lesion can be diagnosed as an early gallbladder carcinoma. In addition, we should evaluate their size, surface structure, internal echo texture, and structural changes of the gall bladder wall. These findings are also useful to discriminate carcinomas from other lesions. Furthermore, abnormal US findings of the gallbladder, which include distension with or without debris and impaired fullness, are also useful to detect occult lesions of the extrahepatic biliary tract.