A dual path ultrasonic flowmeter has been developed in which the measurement of fluid flow and the speed of sound can be made with the same meter without major interdependence. By placing two sound‐speed meters in opposition, sum, and difference frequencies can be extracted. The sum frequency is proportional to the speed of sound and the difference frequency to the velocity of the flowing medium. Small errors which arise from differential path lengths and time delays between the two measuring paths can be minimized by an iterative process of adjustment. Based on this technique, an instrument to measure flow in pipelines was developed and tested. The resulting flowmeter is considered to have an accuracy of 0.25%. By correction for changes in the speed of sound of the measured fluid, the accuracy can be increased to approximately 0.1%.