Three cases of early stage carcinoma of the gallbladder are reported. In two cases, radiolucent shadow was demonstrated on cholecystogram. The masses were papillary adenomas with foci of adenocarcinoma. In the third case, the cholecystogram did not reveal particular findings except for shadows of numerous tiny gallstones. The malignancy was completely unexpected clinically, even after gross inspection of the organ. It was an incidental finding of microscopic examination, which disclosed abundant Rokitansky-Aschoff's sinuses associated with foci of cytologically malignant cells in the muscular layer. It was explained as malignant change of epithelium on one of the sinuses. All three patients underwent simple cholecystectomy. So far they have been free from evidence of metastasis or recurrence. The diagnosis and treatment of early carcinoma of the gallbladder are discussed.