Using standard immunoperoxidase techniques, four cases of malignant sweat-gland carcinoma were examined for the presence of carcinoembryonic antigen (CEA). This substance was universally present in these lesions in spite of their wide spectrum of histologic features. CEA was mainly localized within the cytoplasm of tumor cells and in the lumina of neoplastic glands. The findings indicate that the presence of CEA in malignant skin adnexal tumors could help to identify and categorize these lesions as derived from eccrine or apocrine adnexal epithelium.