We propose to study various antimetabolites with regard to their ability to penetrate human and hairless mouse skin. The biological action of these antimetabolites on epidermal proliferation will be measured in model systems after they are perfected. We are in the process of developing these model systems of epidermal hyperproliferation. The biopharmacology of two drugs, being considered for psoriasis treatment, will be pursued. These drugs are triacetyl azauridine and mycophenolic acid.