Adequate capillary blood flow is a critical parameter for tissue vitality. We present a novel non-invasive method for measuring blood flow based on the acousto-optic effect, using ultrasound modulated diffused light. The benefits of the presented method are: deep tissue sampling (> 1cm), continuous real time measurement, simplicity of apparatus and ease of operation. We demonstrate the ability of the method to measure flow of scattering fluid using a calibrated flow phantom model. Fluid flow was generated by a calibrated syringe pump and the phantom's sampled volume contained millimeter size flow channels. Results demonstrate linear dependence of flow as measured by the presented technique (CFI) to actual flow values with R 2=0.91 in the range of 0 to 2 ml/min, and a linear correlation to simultaneous readings of a laser Doppler probe from the same phantom. This data demonstrates that CFI readings provide a non-invasive platform form measuring tissue microcirculatory blood flow.