The effects of the number of stenoses and the distance between consecutive stenoses on the total pressure drop across a series of noncritical stenoses with 50 percent area reduction were determined experimentally. The mean flow rate was varied to correspond to a Reynolds number range of 30–280 and both in vitro and in vivo measurements of the pressure drop were carried out. Flow visualization studies also were performed. The pressure drop across a series of stenoses was found to increase linearly with the number of stenoses. Comparable results were obtained from the steady and pulsatile flow in vitro experiments as well as from the in vivo experiments. The results indicate that the total effect of a series of noncritical stenoses is approximately equal to the sum of their individual effects and that the combined effect of a series of noncritical stenoses thus can be critical.