To investigate whether or not Paget cells exhibit the same proliferation way as other malignant cells, primary monolayer cultures of epithelial cells from the involved epidermis of mammary and extramammry Paget's disease were carried out. Epidermis was separated from the dermis with dispase, then, epidermal cell suspensions were obtained with EDTA and trypsin.As commercially available media, Keratinocyte SFM or 10% FCS/DMEM were used. Epithelial monolayers could be maintained up to around 45 days. Serial cell lines were not developed from these primary cultures. The percentages of PAS, CEA, EMA positive cells in the cultured cells were not increased progressively. These findings suggest that Paget cells in the involved epidermis do not have potency like other malignant cells.