In 411 patients undergoing cholecystectomy, benign polyps were present in 32 gallbladders and malignant polyps were present in eight. Histologically, cholesterol polyps accounted for most of the benign lesions, and all the malignant lesions were adenocarcinomas. Gallstones coexisted in 50% of the malignant lesions and endoscopic retrograde cholangiography revealed anomalous pancreaticobiliary junctions in three of five patients with malignant lesions. Sixty-nine percent of patients with benign lesions were under 60 years of age, whereas 75% of those with malignant lesions were over 60. Ninety-four percent of the benign lesions were under 1.0 cm in diameter, while 88% of the malignant lesions exceeded this size. Spread and size of the tumor showed a close correlation. Therefore, size of the tumor is a vital indicator in the treatment of polypoid lesions of the gallbladder, and a malignancy should be considered when the tumor exceeds 1.0 cm in diameter.