An assessment of the use of Doppler ultrasound for the measurement of venous blood expelled at the site of the popliteal vein was made. Ten subjects underwent colour Doppler ultrasonography and measurements for peak venous velocities and venous blood volume expelled were taken for each subject when standing and during voluntary contractions. The study shows that only a weak correlation exists between peak venous velocities and venous blood volume expelled, indicating that peak venous velocity alone, is not an accurate measure of the performance of the calf muscle pump either naturally or via artificial means. Furthermore it has been shown that volume measurements based on manually traced intensity weighted mean velocities resulted in large deviations when compared to volume measurements based on computer traced intensity weighted mean velocities.