An in vivo investigation of synthetic aperture flow imaging using a dual stage beamformer is presented in this paper. In the previous work, simulations and Doppler flow phantom experiments showed promising results, which indicated the methods capability of producing fast color flow mapping with a good quality. Due to the continuous data, both high velocity and low velocity can be estimated. Moreover, synthetic aperture flow imaging can be implemented on a commercial platform, because the number of calculations have been reduced. In this work, A commercial ultrasound scanner (Pro Focus equipped with a UA 2227 Research Interface, BK Medical, Herlev, Denmark) was used to transmit signals and record echoes. The data are processed off-line. The method is validated using a pulsatile flow phantom. Volume flow is calculated, and is compared with the volume flow set for the pump. The relative standard deviation is 14.3% and relative bias is 6.4% for the phantom measurements. The blood flow in a common carotid artery of a 35-year-old healthy male is scanned by a medical doctor (PMH). The in vivo data is processed off-line. Fast synthetic aperture color flow mapping with frame rate of 85 Hz is produced and the volume flow is calculated.