The aim of this study was to evaluate the influence of pressure applied while assessing the graft's tightness on the expression of adhesion molecules. Another goal was to find a correlation between the type of fluid (heparynized blood or saline) used during preparation of the conduit and the expression of the adhesion molecules. Saphenous vein fragments were obtained from 48 patients who had undergone coronary artery surgery. Expression of the following particles was evaluated: CD 31, ICAM 1, VCAM 1 and P-selectin. Expression of the CD 31 molecule was described as a percentage of the inner surface of the vessel showing positive immunocytochemical reaction. Expression of the remaining molecules (ICAM 1, VCAM 1, P-selectin) was assessed as the percentage of the surface, determined by CD 31 positive reaction. The expression of the adhesion molecules (ICAM 1, VCAM 1, P-selectin) was higher in the fragments of the vein exposed to pressure. In reference to VCAM 1 the difference, as compared with the control group, was: 250% in the fragments infused with blood and 270% in the fragments infused with saline, respectively. The differences for the ICAM 1 were approximately 300% in both experimental groups and 450% for the P-selectin with subtle differences between the two experimental groups. The loss of the endothelial surface (determined by the expression of the CD 31 antigen) was similar in the specimens flushed either with blood or saline, which indicates that the major cause of damage of the endothelium is influence of pressure on the conduit's wall. Mechanical widening of vessels results in the increased expression of the adhesion molecules on the surface of the endothelial cells, and, as a consequence, leads to rise in the leukocyte adhesion and loss of the functional properties of the transplanted veins.