Thirty-four cases of sarcomatoid carcinoma with minimal epithelial components (SC) and six cases of sarcomatous tumour without any epithelial component (ST) in various organs were studied by the immunoperoxidase technique for the expression of epithelial markers, cytokeratins and epithelial membrane antigen (EMA). Employing antibodies against both high and low molecular weight cytokeratins, sarcomatoid components in 30 examples of SC were stained positively. Epithelial membrane antigen was demonstrated in 19 out of 34 SC. The positive cells for epithelial markers within sarcomatoid components in some cases of SC, which were regarded as originating from squamous cell carcinoma, tended to be seen less frequently than in the tumours derived from adenocarcinoma or transitional cell carcinoma. In six cases of ST, stain for EMA was negative and stain for cytokeratins was positive in three examples. The immunohistochemical examination of epithelial markers in the tumours of these types may be of value in differentiating these tumours from true sarcomas.