Aim To investigate the effects of blockers of the three kinds of potassium channels: voltage dependent K + channel(K V), calcium activated K + channel(K Ca ) and ATP sensitive K + channel(K ATP ), on the proliferation of rat bronchial smooth muscle cells (BSMCs). Methods The effects of three kinds of potassium channel blockers on the proliferation of BSMCs were detected by MTT method, immunocytochemistry staining and flow cytometry. Their effects on the dynamic changes of Ca 2+ concentration in BSMCs were investigated by the fluorophotometry of Fura 2/AM. Results The K V blocker 4 aminopyridine (4 AP) was shown to significantly increase the expression of proliferating cell nucleus antigen in cultured rat BSMCs ( P <0 01), but the K Ca blocker tetraethylammonium (TEA) and K ATP blocker glibenclamide(Glib) did not show such effect ( P >0 05). 4 AP was found to significantly increase the optical density value of the cultured BSMCs ( P <0 01) by MTT method and the numbers of S+G 2M BSMCs( P <0 05) by flow cytometry. TEA and Glib did not show such effects. 4 AP significantly increased the Ca 2+ concentration in cultured BSMCs( P <0 01). TEA and Glib did not show such effects. Conclusion This result suggests that inhibition of K V activity can increase intracellular Ca 2+ and proliferation of rat BSMCs, but inhibition of K Ca and K ATP showed no effect.