A new ultrasound instrument has been developed, using vector Doppler and embedded machine intelligence, to enable measurement of access flow rates by non-specialists. Ultrasound measurement of access flow can be performed with the patient off the dialysis machine, avoiding the hemodynamic changes that may affect indicator-dilution methods. A research version of the instrument was tested on flow phantoms simulating graft flow, and showed accuracy better than 5%. A non-specialist measured flow in the access grafts of 7 consenting dialysis patients; the instrument showed flows commensurate with indicator-dilution-measured flows, but with less variability. Measurements were made in less than 5 min per patient. The cost per measurement is calculated to be significantly less than that of present methods of measuring flow. The new instrument may become a useful tool for monitoring flow in accesses to extend their life.