Objective: To examine the role of cytokines in cervical dilation. Methods: In 55 patients undergoing cesarean delivery, we took samples from the lower uterine segment, the decidua, and the membranes. We determined the concentrations of interleukin (IL)-2, IL-8, tumor necrosis factor-α, matrix metalloproteinase (MMP)-8, and MMP-9 in the different tissues. Results: Depending on the state of labor, we observed a significant increase (P < .001) in IL-8 concentrations in the lower uterine segment. The leukocyte enzymes MMP-8 and MMP-9 were highly significantly correlated with the IL-8 concentrations. Conclusion: Interleukin-8 is critically involved in the process of parturition in humans. Interleukin-8 concentrations in the myometrium, decidua, and membranes correlated strongly with the observed MMP-8 and MMP-9 concentrations.