Abstract: Three cases of extramammary Paget disease of the scrotum and penis were reported. Histopathologically, they were confirmed as infiltrating carcinoma, Ultrastructures of Paget cells and their plasma membranes were observed by freezeetching electron microscopy.The Paget cells are characterized by larger cells with round or oval nuclei enclosed by a slightly undulated nuclear membrance. They include abundant cytoplasmic Golgi appasatus, endoplasmic reticulum, occasionally larger mitochondria and vacuoles, but lack of tonofilaments. The microvilli and vesicles were seen in the inercellular spaces between two Paget cells. No ga.p junction were found between two Paget cells as well as between Paget cells and adjacent keratinocytes, occasionally desmosomes were observed. While more gap junctions than that in normal skin and normal desmosomes were found between two adjacent keratinocytes.