Background: Ischemia is one of the most common causes of anastomosis disruption. In the present study we investigated the effect of locally injected recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) on ischemic bowel anastomosis in rats. Methods: 144 male Sprague-Dawley rats were randomized into four groups: in group 1, colon anastomoses were performed; in group 2, anastomoses were performed then 50 µg rhGM-CSF was injected subserosally into the perianastomotic area; in group 3, anastomoses were performed on ischemic colon segments, and in group 4, colon anastomoses were performed on ischemic segments and then 50 µg rhGM-CSF was injected subserosally into the perianastomotic area. On the 3rd and 7th post-operative days, the rats were sacrificed and anastomotic bursting pressures were measured. Hydroxyproline contents were studied on the tissues from the anastomotic line. Three anastomotic segments were saved from each group for histopathological studies before bursting pressure measurement. Results: The bursting pressure in group 3 was significantly weaker than in the other groups. There were no significant differences between the bursting pressures in groups 1 and 4. The levels of hydroxyproline content in group 4 were significantly greater than in group 3. Conclusions: These data suggest that the local injection of rhGM-CSF improves the healing of ischemic and even normal colon anastomoses.