Two cases of heterotopic tissue involving the gallbladder are presented (one gastric mucosa, the other liver), and the relevant literature is reviewed highlighting problems in differential diagnosis and complications, particularly with regard to gastric mucosal heterotopia. A firm diagnosis of gastric heterotopia is based on the presence of fundic mucosa replete with parietal and chief cells; a clear distinction from intestinal metaplasia should be made, but at times may be difficult. Potential complications include mucosal ulceration, obstruction, and hemorrhage. Of 39 patients presented, about half were 30 years of age or younger, and only nine have had calculi noted in the cholecystectomy specimen. Heightened awareness of gastric heterotopia with separation of smooth-muscle bundles may help to avoid a malignant diagnosis. Hepatic tissue involving the gallbladder that is completely separate from the main part of the liver is an even rarer form of heterotopia that should be distinguished from an accessory lobe.