The purpose of this study was to assess the viability and dilator response of the saphenous vein segments harvested during cardiac surgery. The saphenous veins were incubated with either normal saline (group A) or papaverine solutions (group B). The viability of saphenous vein endothelial cells was assessed by counting the number of total cells. Maximal endothelium-dependent vasodilator response to acetylcholine was also investigated. Cell viability of vein samples was decreased after 4 hours of incubation with normal saline (34 +/- 6.5%) as compared to solution containing papaverine (92 +/- 3.7%). By 24 hours, the viabilities of the endothelial cells incubated with saline and papaverine solutions were 22 +/- 4.5% and 87 +/- 5%, respectively.There was significant difference in vasodilatation responses to acetylcholine between saline-incubated and papaverine-incubated groups. By 4 hours of incubation, the relaxation response to acetylcholine significantly deteriorated in group A when compared to the initial value (P < 0.001). Furthermore, the decrease in this vasorelaxation response has also continued throughout the observation period and the values obtained by 24 hours were observed to be significantly lower than those obtained at the end of 4 hours (P < 0.01). In contrast, although a decrease was noticed in group B over time, this decrease was not statistically significant (P, not significant). We thus conclude that the use of papaverine solution improves endothelial cell viability and is associated with preservation of the maximal endothelial-dependent vasodilator response of a vein segment.