This study examined the effects of exposure to arterial blood pressure and flow on human saphenous vein catecholamine sensitivity. Unused portions of saphenous vein from eight patients undergoing peripheral bypass procedures were mounted parallel in a specially designed organ culture apparatus and perfused with tissue culture medium with 95% CO2 at 37°C. One segment was fixed between two cannulas while the medium was gently agitated (control) and the other was actively perfused via a pulsatile pump system at a rate of 60 beats/min, peak pressure of 100 mmHg and peak flow of 200 ml/min (pulsed; mean pressure 60 mmHg; mean flow 115 ml/min). After 48 h, vein segments were removed and tested for in vitro isometric contraction in response to KCI, norepinephrine and histamine, and relaxation in response to acetylcholine, calcium ionophore A23187, and sodium nitroprusside. There were no differences in mean(s.e.m.) maximal contraction in response to KCI (control 0.61 (0.16) g versus pulsed 0.72(0.27) g; P = n.s.), norepinephrine (control 1.00(0.56) g versuspulsed 1.51(0.54) g;P = n.s.), or histamine (control 1.47(0.85) g versus pulsed 1.95(0.64) g; P = n.s.). However, pulsed veins exhibited increased sensitivity to both norepinephrine (control −logED50 6.20(0.23) versus pulsed mean(s.e.m.) 6.60(0.17); P < 0.05) and histamine (control −logED50 5.60(0.27) versus pulsed 6.24(0.20); P = 0.05). Pulsed veins exhibited slightly less acetylcholine-induced relaxation although the difference did not reach statistical significance (control mean(s.e.m.) relaxation at 1 × 10−6M 9.2(14.0)% versus pulsed −13.3(6.4)%; P = n.s.). There were no differences in relaxation in response to either A23187 (control 1 × 10−4M 178(19)%versus pulsed 191(68)% or sodium nitroprusside (control 225(15)% versus pulsed 254(17)%;P = n.s.). The data presented herein indicate that exposure of human saphenous vein to the hemodynamics of the arterial environment for 48 h results in catecholamine supersensitivity while contractile and relaxant function are not affected.