In an attempt to characterize the immunocytochemical attributes of eccrine sweat gland carcinoma, we studied 32 examples of this tumor with antibodies to epithelial membrane antigen (EMA), cytokeratin (CK), carcinoembryonic antigen, S100 protein, alpha-lactalbumin, salivary amylase, blood group isoantigens, beta-2-microglobulin, and Leu M1. All cases expressed EMA and CK, and 28 of 32 cases also displayed at least 2 of the 6 remaining antigens. No significant variations were noted in the immunophenotypes of histologic subtypes of eccrine carcinoma. These results provide an objective means of diagnostic separation between sweat gland carcinoma and other primary malignant cutaneous tumors. However, they do not appear to correlate with the degree of tumoral differentiation, and are of no assistance in the separation of benign and malignant sudoriferous neoplasms. The ability of immunocytochemical techniques to distinguish between primary malignant adnexal cutaneous tumors and metastases to the skin appears unlikely, but remains to be studied further. Also, the use of immunostaining panels is advised in the study of adnexal carcinomas, since no single determinant in isolation is specific for these neoplasms.