Secretion of proinflammatory cytokines IL-1βp, TNF-α, IL-6, IFN-α, and IFN-γ by the chorion tissue (8-12 weeks) was studied in normal gestation and spontaneous abortion. The production of IL-1β, TNF-α, and IFN-α virtually did not change in spontaneous abortion, while IFN-γ was not secreted in all experimental groups. The production of IL-6 increased more than 2-fold in patients with spontaneous abortion during the first trimester. These data confirm the involvement of this cytokine in the reproductive processes and in the pathogenesis of miscarriage.