This study examines the extent of endothelial damage following a period of irrigation with various crystalloid irrigation fluids. Both arteries and veins were evaluated after irrigation with normal saline, lactated Ringer's, Balanced Salt Solution (BSS), and Balanced Salt Solution Plus (BSS+). The arterial and venous endothelia were examined with the scanning electron microscope. Using a randomized blind observer scoring system, micrographs were evaluated for changes in nuclear shape, cell junction integrity, cytoplasm changes, and sloughing of the endothelial cell layer. BSS+ and BSS produced statistically significant (P less than .001) improvement over the other two irrigation fluids in the arteries. BSS+ and BSS were statistically superior (P less than .001) in the venous vessels. The compositions of BSS and BSS+ tend to maintain a physiologic environment in the presence of ischemia. These fluids maintained a morphologic appearance closer to that of perfusion-fixed controls. The data suggest a protective effect of such physiologic preparations on the endothelium. The preservation of intact endothelium may play a role in decreased platelet activation, continued production of prostacyclin, and maintenance of an intact barrier between the intracellular and extracellular spaces. This could enhance the survival of transplanted or transferred tissue, by helping to maintain nearly normal endothelium during surgery.