We investigated the expression of both epidermal fatty acid-binding protein (FABP5), a marker of transit amplifying cells, and nestin, a putative marker of epidermal stem cells, in psoriatic epidermis and in normal human cultured keratinocytes. In lesional psoriatic epidermis, immunostaining showed that the suprabasal layer was positive for nestin, with some cells co-expressing FABP5. Flow cytometric analysis revealed that the expression of both nestin and FABP5 were increased in keratinocytes cultured in a low concentration of calcium relative to those cultured in a high concentration of calcium. These results suggest that nestin and FABP5 are expressed in actively proliferating keratinocytes in vitro and in the suprabasal layer in lesional psoriatic epidermis, and that double-positive cells may identify transit amplifying cells in the epidermis.