Involved psoriatic epidermis maintains its histologic appearance, increased labeling index, and increased level of plasminogen activator after grafting onto athymic nude mice. Epidermis from clinically uninvolved psoriatic skin develops an increase in plasminogen activator activity after grafting for 6 weeks on nude mice and demonstrates an increased labeling index. Normal control skin maintains its low level of plasminogen activator and labeling index after grafting. These results indicate that psoriatic skin can maintain and develop markers of psoriatic skin independent of the host.