The use of High-Frequency Pulsed Doppler Ultrasound (HFPDU) for evaluation of microvascular hemodynamics is well established. Due to technical limitations of existing probes, quantitation of anastomotic stenoses and detailed waveform analyses are difficult to perform and impractical for clinical use. We present a new Tandem Doppler Probe (TDP) for simple and accurate study of blood flow in vessels smaller than 1 mm in diameter. Its unique ability to compare the pre- and post-anastomotic waveforms simultaneously allows for quantitative detection of anastomotic narrowing of as little as 5%, as well as identification of subtle pathologic anastomotic waveform changes not seen with single probes. Such early and precise delineation of anastomotic problems in the operating room can provide an invaluable, objective assessment of the technical adequacy of the anastomoses as well as an important baseline for later post-operative monitoring of free-tissue transfers with implantable Doppler devices.