Backgrounds : Pityrosporum (P.) ovale is a member of the cutaneous microflora, and is associated with several dermatologic diseases. Little is known about the mechanism by which P. ovale causes these dermatoses, but it has been supposed to be associated with immunologic response. The epidermis is largely composed of keratinocytes, and they not only play an important structural part in forming a physical barrier to microorganisms, but also are important functionally in mediating cutaneous immune reaction by secreting various cytokines. Objectives : There have been few studies on the interaction between fungi and keratinocytes, especially the effect of P. ovale on the production of cytokines by human keratinocytes. This study is to evaluate the effects of P. ovale on pro-inflammatory cytokines such as interleukin-lα (IL-lα), tumor necrosis factor-α (TNF-α), granulocyte-macrophage colony stimulating factor (GM-CSF) producted by human keratinocytes. Methods : Normal human keratinocytes (NHK) from neonatal foreskin were suspended in culture medium with different concentrations of the P. ovale extract (0.01, 1, 10, 100㎍/㎖). The production of IL-lα, TNF-α and GM-CSF after 24 hours treatment were somiquantitated by RT-PCR. Time-course changes of the cytokines were also observed until 72 hours (0, 6, 12, 24, 48, 72 hours). NHKs were treated with P. ovale culture supernatant (0.1, 0.2, 0.5, 1.O㎖) for 24 hours, and the cytokines were measured by RT-PCR and ELISA. Results : IL-lα and GM-CSF were increased by treatment with P. ovale extract as a dose-dependent manner. But TNF-α production was not affected by the treatement. The level of IL-1α was steadily increased with its maximum at 48 hours. The level of GM-CSF was increased for 48 hours and became decreased thereafter. NHKs treated with P. ovale culture supernatant showed the increase of IL-lα and GM-CSF synthesis as a dose-dependent manner. Conclusions : P. ovale induced the pro-inflammatory cytokines in normal keratinocytes, which is supposed to induce inflammatory response by the organism in the skin. (Korean J Dermatol 2003;41(11) : 1448∼1454)