Intermittent hypoxia increased chemotaxis of monocytes with IL-8 dependence. THP-1 cells were treated with normoxia or intermittent hypoxia for one, three and six cycles, and the culture medium was collected as the attractant for the following chemotaxis process. Chemotaxis of the monocytic THP-1 cells toward IL-8 was analyzed by means of the transwell migration assay for 1 h toward the condition medium of the IH-treated THP-1 cells. (a,b) The number of THP-1 cells that were attracted by IL-8 and migrated through the transwell filter was increased by intermittent hypoxia and diminished by the anti-IL-8 antibody-pretreated conditioned medium. A control experiment to exclude the pure IgG effect with an unspecific antibody “mouse IgG1, Kappa Monoclonal (NCG01)-Isotype Control-BSA and Azide Free” was conducted, which showed no effect on the IL-8-induced migration. Note: The data were presented as the means and the standard errors from three independent experiments, * p < 0.05 vs. normoxia; † p < 0.05 vs. six IH cycles with anti-IL-8; ‡ p < 0.05 vs. one IH cycle; § p < 0.05 vs. three IH cycles. Abbreviations: IH = intermittent hypoxia; IL = interleukin.