The NeuroDop is a new bedside assessment tool consisting of a continuous wave ultrasound probe attached to a stethoscope earpiece. This study was designed to compare middle cerebral artery (MCA) velocity assessment obtained with the NeuroDop versus standard transcranial Doppler (TCD). TCD technologists performed continuous wave NeuroDop studies followed by standard TCD studies on 60 subjects. Technologists recorded presence of MCA signal and estimated velocity based on NeuroDop auditory characteristics. Signal was obtained in 108 MCA vessels with the portable unit and in 112 vessels using standard TCD. For detection of patency, sensitivity was 96%, specificity 88%, positive predictive value 99%, and negative predictive value 58%. Auditorially estimated velocities from the NeuroDop strongly correlated with TCD velocity measures (r = 0.71). Categorical estimates of velocity as decreased (< 37 cm/sec), normal (37-81 cm/sec), or increased (> 81 cm/sec) demonstrated an accuracy rate of 85%. This novel stethoscope-continuous wave unit has excellent sensitivity in detecting presence of MCA patency. Moreover, MCA velocities can be characterized to a reasonable degree of accuracy based on NeuroDop auditory characteristics. The NeuroDop shows promise as a tool to rapidly assess and serially monitor presence and amplitude of MCA velocity and may help guide thrombolytic and other emergency management decisions in stroke patients.