The present study was done to determine the effect of the modified Hall valvulotome technique on endothelial injury by measuring TxB2 and 6-keto PGF1alpha, the stable metabolites of thromboxane and prostacyclin, respectively. It was hypothesized that increased levels of these cyclooxygenase products would be an excellent indicator of vascular endothelial injury in the presence of the modified Hall valvulotome. Eight segments of human distal saphenous veins were obtained, each measuring approximately 4 cm in length, with diameters of approximately 2 to 3 mm. From these original vein segments, two groups of smaller vein segments were examined, with each group consisting of eight segments, each segment measuring 2 cm in length. The first group of vein segments was designated as the control group, and the second group of vessels had a modified Hall valvulotome (2.5 mm size) inserted into each segment to simulate valvulotomy. After this procedure, all vein segments were analyzed for levels of thromboxane and prostacyclin by a standard radioimmunoassay procedure. Results from the present study indicate that the modified Hall valvulotome technique in human saphenous veins does not significantly increase the levels of the cyclooxygenase metabolites thromboxane and prostacyclin relative to control conditions. However, the ratio of TxB2 formation 6-keto PGF1alpha production was increased in the valvulotomized vessel segments, indicating possible platelet release of thromboxane. Therefore, even though there was increased thromboxane production relative to prostacyclin levels in the modified Hall valvulotome technique, it still appears that this type of valvulotomy is relatively noninsulting to the endothelial cell lining.