The production of interleukin-1 (IL-1) and interleukin-1 inhibitor by keratinocytes isolated from the skin of epidermodysplasia verruciformis patients was studied. Keratinocytes from uninvolved skin of patients with most pronounced neoplastic lesions produced large amounts of an IL-1 inhibitor (20-40 kD). Keratinocytes from preneoplastic lesions showed no significant differences compared to cells from healthy donors but their production of IL-1 after UVB irradiation was increased.