Aim To observe the synergistic effect of basic fibroblast growth factor and interleukin-6 on vascular smooth muscle cells proliferation. Methods BrdU incorporation and cell counting method were adopted to observe the effects of basic fibroblast growth factor and interleukin-6 on the proliferation of rat aortic cultured smooth muscle cells. Results 0～10.0 μg/L basic fibroblast growth factor and 0～100 μg/L interleukin-6 were able to promote smooth muscle cells proliferation separately, and synergistically in combination in dose- and time-dependent manner. The pro-proliferation effect reached climax at 24 hours. Conclusion Basic fibroblast growth factor and interleukin-6 had synergistic effect on vascular smooth muscle cells proliferation.