The activities of eight enzymes were determined by fluorometric micromethods in epidermal tumors (basal and squamous cell epithelioma, verruca seborroeica and keratoacanthoma) and compared to the activities in the adjoining, apparently normal epidermis. The activities were increased in basal cell epithelioma, variable in squamous cell epithelioma and verruca seborroeica and lowered in keratoacanthoma.