The presence and distribution of carcinoembryonic antigen (CEA) and lectin-binding sites in benign apocrine sweat gland tumours was investigated using immunoperoxidase and immunofluorescent techniques respectively. CEA was present in apocrine hidrocystoma, hidradenoma papilliferum, and syringocystadenoma papilliferum. The distribution pattern of CEA was indistinguishable in each of the three types of tumour. The distribution of lectin-binding sites was similar in all cases of a given type of neoplasm, and the staining patterns were similar but not identical in hidradenoma papilliferum and syringocystadenoma papilliferum. However, the distribution of lectin-binding sites in apocrine hidrocystoma was different. These results could be useful in elucidating the nature of the cells of origin of benign apocrine sweat gland tumours and providing a basis for their classification.