It has been suggested that peripheral vascular resistance (PR), measured intraoperatively, can predict the outcome of infrainguinal reconstructions. There is, however, a great deal of variability in design and predictive value with this method, and it is prone to technical difficulties and possible errors. The present study evaluated the influence of the choice of infusion medium and the back pressure on PR as measured by the infusion technique. In a porcine model of experimentally induced stenosis, standard PR (calculated by the pressure difference across the stenosis and the Doppler volume flow) was compared with PR based on infusions of blood or saline solution. With blood as the infusion medium there was a significant correlation between the PR and the standard values (r = 0.795, p = 0.0005), whereas there was no correlation when saline solution was infused (r = 0.067, p = 0.345). Subtracting the back pressure resulted in a slight improvement in the correlations between standard PR and PR measured after infusion of blood but not saline solution. In summary, blood should be used as an infusion medium in methods of PR determination, but the influence of back pressure remains uncertain.