Neutrophil infiltration is known to affect the endothelial monolayer of seeded vascular grafts. The aim of this study was to develop an in vitro system allowing the monitoring of neutrophil (PMN) adherence after graft implantation. Dacron prostheses were seeded with autologous canine microvascular cells from omental adipose tissue and implanted for 35 days. In vitro, mature monolayers of canine homologous venous endothelial cells (CHVENC) were exposed to heparinized whole blood samples taken at days one and four postoperatively, followed by weekly tests. PMNs adherent to the CHVENC were counted per culture area. Results showed the feasibility of PMN monitoring, and demonstrated a late PMN adhesion, reaching its maximum about 20 days after implantation and decreasing to normal values after five weeks. It is concluded that in vitro tests can be used for noninvasive studies of host plasma factors and leukocyte activation.