The effects of intradermal injection of interferon α-2β on normal human skin were studied in 12 healthy adult volunteers using 500,000 international units recombinant human interferon α-2β, 3 times a week for five injections (n = 6) and nine injections (n = 6). Saline injections served as control sites. Lymphocytic infiltrates and the population of epidermal Langerhans' cells in the injection areas were observed. The results showed that epidermal Langerhans' cells (both adenosine triphosphatase positive and CD-1+) decreased significantly whereas human leukocyte antigen-DR expression in keratinocytes was enhanced. Dermal CD-3+ (Pan T cells), CD-4+ (T helper cells) and human leukocyte antigen DR+ cells increased. No significant differences in the number of CD-19+ (B cells) and CD-57+ (NK cells) were observed. There were no significant differences between the five-injection and nine-injection groups.