Inferior vena cava flow (IVCF) and abdominal aortic flow (AAF) are seems to be affected by gravity, ie., it depends on the body posture. We validated the effect of gravity on IVCF and AAF in supine and upright positions using an original multi-posture MRI. IVCF/AAF mean velocity, IVCF/AAF maximum velocity, mean IVCF/AAF, maximum IVCF/AAF in the upright position were significantly lower than those in the supine position. The cross-sectional area of IVC was significantly lower than those in the supine position, but that of AA was not significantly changed. Both IVCF and AAF decrease in the upright position.