Expression of human involucrin (hINV) a protein of the cornified cell envelope, was studied in the skin of gasoline storage workers, in order to evaluate the effects of the exposure to petroleum derivatives. A total of 25 forearm skin punch biopsies were carried out. Twenty of which were performed on exposed subjects and five on controls. The specimens were processed for immunohistochemistry and hINV expression was evaluated using an anti-hINV monoclonal antibody and the ABC technique. Percentage of immunolabeled keratinocytes was significantly higher in subjects exposed to gasoline with respect to the control sample. A premature hINV expression was detected both in suprapapillary and interpapillary keratinocytes. Such overexpression of hINV seems to be related to an attempt of increasing skin defence mechanism. Therefore it was concluded that also in absence of clinical skin manifestation the exposure to gasoline determines an involvement of keratinocytes on molecular basis.