PROBLEM: We measured interleukin-8 (IL-8) and granulocyte counts in cervical mucus to assess local immunity and parturition. METHOD OF STUDY: We detected IL-8 by enzyme linked immunosorbent assay (ELISA) and Western blotting. Granulocytes were counted on a slide glass containing mucus from the external cervical os. RESULTS: ELISA and Western blotting revealed IL-8 in cervical mucus from both nonpregnant and pregnant women. There were no significant differences in cervical mucus IL-8 levels or granulocyte counts between follicular, ovulatory, and luteal phases. However, IL-8 and granulocyte counts were significantly decreased after menopause. IL-8 and granulocyte counts were increased significantly during pregnancy, and were further increased after 38 weeks of gestation and at labor. IL-8 levels were significantly correlated with granulocyte counts, based on the study of 678 samples (P<0.0001). CONCLUSION: IL-8 is involved in the increase of cervical granulocytes and in the process of parturition.