Abstract： Background The dysfunction of vascular endothelial cells plays a key role in starting and facilitating restenosis. The acceleration of intima repair and the recovery of endothelial function would reduce the restenosis rate. This study was undertaken to assess the effect of granulocyte-macrophage colony stimulating factor (GM-CSF) on the repair of damaged iliac arteries.Methods Twenty-four male New Zealand white rabbits undergoing primary iliac artery deendothelialization were randomly divided into two groups (GM-CSF group and control group). The GM-CSF group received a subcutaneous injection of GM-CSF (10 μg·kg-1·d-1), and the control group was given a subcutaneous injection of equivalent saline. The iliac arteries of all animals were damaged by balloon after 7 days. The levels of nitric oxide (NO) were detected before, 1 week, 2 weeks and 4 weeks after angioplasty. The repair and hyperplasia of the intima were observed microscopically and the indices of stenosis were evaluated by computerized planimetry after 4 weeks of angioplasty.Results The NO levels of the GM-CSF group were higher than those of the control group 2 weeks and 4 weeks after angioplasty [(91.92±11.57) μmol/L vs. (81.67±12.18) μmol/L; (97.67±10.13) μmol/L vs. (83.16±12.64) μmol/L]. Four weeks after balloon damage, histological examination showed that neointima formation, vascular smooth muscle cells and fibrous tissue of the GM-CSF group were less than those of the control group. The endothelium of the GM-CSF group was more integrated, and stenosis of lumen was slighter than that of the control group. Morphometry showed the lumen area of the GM-CSF group was larger than that of the control group [(1.27±0.31) mm2 vs. (0.92±0.24) mm2], the neointimal area and percent of intima hyperplasia were significantly smaller than those of the control group [(0.85±0.34) mm2 vs. (1.18±0.38) mm2; (40±7)% vs. (55±6)%].Conclusion GM-CSF could facilitate the repair of the intima, reduce neointima formation, better the function of the endothelium, and decrease the rate of restenosis.