A case of adenosquamous carcinoma of the gallbladder showing extensive spindle transformation is presented. By light microscopy, areas showing interwoven fascicles of fusiform, poorly differentiated cells closely resembling a sarcoma were seen to merge imperceptibly with areas showing more obvious glandular and squamous cell features. Immunocytochemistry utilizing tissue-specific antibodies against intermediate filaments demonstrated the exclusive presence of prekeratin antibodies in both components of the tumour, thus establishing the epithelial nature of this neoplasm. The importance of immunological phenotyping in the differential diagnosis of epithelial tumours of the gallbladder showing pseudosarcomatous features is underscored.