Background. Intraperitoneal chemotherapy (IPCT) is an alternative local adjuvant treatment for patients with resectable colonic and gastric cancers. This is the simplest and safest method for systemic toxicity, but it can affect the healing of colonic anastomoses. Granulocyte macrophage-colony stimulating factor (GMCSF) may be used to prevent this side effect by means of macrophage activity stimulation. Methods. In this experimental study the effects of early postoperative intraperitoneal 5-fluorouracil (5-FU) and local administration of recombinant human GM-CSF (rGM-CSF) were studied on rats. The anastomotic bursting pressures, hydroxyproline contents of tissues, and histological appearance were assessed. Results. It was found that anastomotic healing of colon was impaired after intraperitoneal 5-FU administration, but when rGM-CSF was injected to the both sides of the anastomoses locally, this side effect could be prevented. Conclusion. IPCT may diminish the activity of macrophages and impair the wound healing; locally applied rGM-CSF enhanced wound healing on colonic anastomoses. (C) 2002 Elsevier Science (USA).