Abstract: A dual ultrasonic transducer probe and a method of utilizing the probe to determine a blood vessel diameter are presented. The probe comprises first and second ultrasound transducers whose ultrasound beams intercept at an acute angle, and which can be so disposed relative to a blood vessel's longitudinal axis that both their ultrasound beam axes intercept the blood vessel's longitudinal axis. The blood vessel diameter determination method is based on the creation of a two-dimensional matrix of complex reflection amplitude values for each of the beams along an axis of its propagation.