Ultrasonic findings of 7 cases with porcelain gallbladder and a pitfall in differential diagnosis were discussed. Seven cases were all females (age: 40-74, average 59.4). In all cases, ultrasound demonstrated a hyperechoic arc with posterior acoustic shadow. In 5 cases gallbladder lumen and posterior wall were entirely obscured and US differentiation from full cavity gallstone was difficult. In the other 2 cases, gallbladder lumen was partially demonstrated among hyperechoic anterior and posterior wall with acoustic shadow and tumor with gallstone was seen in one of these 2 cases. In this case gallbladder tumor was revealed in laparotomy. Cholecystectomy was carried out in another two cases and pathological diagnosis was chronic cholecystitis without malignancy. In all cases abdominal plain X-ray films demonstrated characteristic calcification. Computed tomography was also done in 5 cases and revealed gallbladder lumen as well as wall calcification. In the case with gallbladder tumor CT findings matched with ultrasonic appearances. CT clearly demonstrated gallbladder lumen without mass lesion in the two cholecystectomy cases in which gallbladder lumen was entirely obscured by acoustic shadow due to wall calcification in ultrasound. Some critical points in the treatment of porcelain gallbladder were also discussed in consideration of our results.