The effects of arterial compliance on stenotic hemodynamics were examined in an in vitro arterial preparation. Carotid arteries, obtained from anesthetized mongrel dogs (11.3-15.4 kg), were attached to a perfusion apparatus consisting of a constant pressure reservoir and a fixed distal resistance. To create an intraluminal stenosis, a balloon catheter was partially inflated within the artery. Pressures proximal and distal to the arterial segment and flow through the arterial segment were measured. Stenotic resistance was calculated as the pressure gradient across the stenosis divided by the flow. Using this preparation, stenotic resistance was shown to be dependent on perfusion pressure and peripheral resistance. Decreasing the perfusion pressure from 141 ± 1.4 to 78 ± 0.3 caused stenotic resistance to increase from 0.72 ± 0.10 to 9.10 ± 1.18 mm Hg·ml-1·min (p < 0.01). Reducing the peripheral resistance caused stenotic resistance to increase from 1.16 ± 0.22 to 2.37 ± 0.29 (p < 0.05). Further, these arterial stenoses present in the compliant artery were unstable. In striking contrast, fixed stenoses, obtained by replacing the artery with a glass rod, were stable and not affected by perfusion pressure or peripheral resistance. Dynamic stenoses respond differently than fixed stenoses to the same interventions.