The systemic administration of granulocyte-macrophage colony-stimulating factor (GMCSF) is used clinically to increase circulating neutrophils, but its wound healing effects after intraperitoneal treatment have not been studied yet. We planned to investigate the effect of neutrophils on wound healing under cyclophosphamide and GM-CSF treatment. Forty rats were divided into three groups: control group (group I, n = 12) receiving saline, group II (n = 14) receiving cyclophosphamide and group III (n = 14) receiving GM-CSF. The rats in all groups underwent incisional wounding and were euthanized after 7 days. Blood neutrophil counts and functions, tensile strengths and the hydroxyproline level of skin were determined, and a histopathological evaluation of healing was made. Neutrophil counts and phagocytosis significantly increased in group III and decreased in group II. Although the skin hydroxyproline level did not differ, there was a difference in tensile strength of the wounded skin between group II and group III. The wound score in group II was lower than that in groups III and I. As a result we suggest that systemically given GM-CSF - by increasing the neutrophil count and neutrophil phagocytosis index - can enhance the tensile strength of surgical incisions. Copyright (C) 2001 S. Karger AG, Basel.