Objective To explore effects of the connexin on the Ca SUP>2+/SUP> -mediated migration and invasion of breast cancer cells. Methods MDA-MB-231 and MCF-7 cells, with high and low metastatic potentials, respectively, were treated with a safe concentration of octanol (100μmol/L) for 24 hours. The morphology change was observed under an inverted phase contrast microscope.The location ofconnexin43(Cx43), arrangement of microfilament(MF)and concentration of intracellular Ca SUP>2+/SUP> were determined by confocal microscopy, and cell migration was checked by wound healing and Transwell chamber assays. Results Functional blockade of gap junctions during the formation of a cellular monolayer resulted in discordance of actin stress fibers between neighboring cells, even though whole-cell morphology of these cells did not change. Confocal microscopy revealed that immunoreactivity of Cx 43 was in the cell membrane，particularly at the region of cell-to-cell apposition regardless of the presence of gap junction inhibition. The number of MDA-MB-231 cells was significantly increased in migration assays, as compared with the control. The concentration of intracellular Ca SUP>2+/SUP> was significantly decreased. EGTA treatment enhanced the inhibition of cell migration and invasion which induced by octanol alone. However, inhibition had no effects on the migration and invasion of low metastatic potential MCF-7cells. Conclusion These data imply that gap junctional inhibitor does not interrupt the formation but rather the function of gap junctions, and the underlying mechanism may be related to the decrease of intracel