The hypothesis of this study was:  Blood flow in the microcirculation can be assessed by US-induced destruction and measurements of refilling curves of Ultrasound Contrast Agents (UCA), acquired using a new modality -Subharmonic color Doppler (SCD). The goals of the study were:  To quantify perfusion at low velocities using UCA and SCD with different vessel widths and contrast microbubbles concentrations. The experiments were performed on two flow phantoms: A 1.2mm tube and Perfusion Dialysis  cartridge. With both phantoms, refilling curves were obtained using different UCA concentrations, and different flow rates. Another experiment was performed to assess the influence of the emission power. The relation between color area and time interval was assumed to follow the function: . The model provided an excellent fit to the obtained data (r>0.98), in all experiments with both phantoms. Higher flow rates correspond to faster replenishment with a steeper slope of the replenishment curve and to a higher β value.  An excellent correlation (r>0.9) between flow rate and β values was found. The results of the experiments made with both phantoms, demonstrate that there are no significant differences between the slopes (P>0.05), but in the elevation (P<0.05) of the regression lines. The impact of the emission power on replenishment kinetics: the values of both parameters A and β increased significantly (P<0.001) with increasing MI, approaching a plateau value at the higher MI’s. Our main finding is that it is possible to assess blood flow in the microcirculation using SCD.