Sonographic findings in 16 patients (10 women, six men) with surgically documented gallbladder carcinoma are reported. Two principal forms are described: localized infiltrating, or fungating, tumors (eight patients) and diffuse tumors infiltrating the entire gallbladder wall (eight patients). In all cases, the tumors were adenocarcinomas. Eleven patients also had cholelithiasis. Contiguous extension and metastasis did not correlate with tumor size. The difficulties encountered an the differential diagnosis are discussed in relation to the different sonographic appearances.