OBJECTIVE Holodiastolic arterial blood flow is associated with pathological conditions. Nevertheless, we have observed that lifting the arm at an angle greater than the horizontal causes holodiastolic arterial blood flow in the brachial artery in normal patients. Thus, we decided to assess the frequency and characteristics of this phenomenon. METHODS Ten volunteers (7 women) aged 43 ± 17 years participated in the study. We used an ultrasound scanner with a 12 MHz probe to analyze the brachial artery. The examination included: a) Baseline measurements in the supine position; b) measurements during three minutes with the arm raised, and c) a measurement sixty seconds after lowering the arm to the supine position in which the baseline measurements had been obtained. RESULTS We observed mid- and end-diastolic retrograde flow in 8/10 patients when their arms were raised. No mid- or end-diastolic retrograde flow was observed in the baseline measurements or after the arm was lowered to the supine position (p=0.0007). The minimum diastolic velocity was significantly higher in the measurements obtained with the arm raised than in the supine position before or after arm raising (-13.5 ± 4.9 cm/s vs. -2.38 ± 7.5 cm/s, p<0.05 and -13.5 ± 4.9 cm/s vs. -4.6 ± 5.2 cm/s, p<0.05, respectively). The modified resistance index was significantly higher when the arm was raised (1.20 ± 0.07 vs. 1.04 ± 0.15; p<0.05); moreover, the modified resistance index was significantly lower in the measurements obtained after the arm was lowered than in the baseline measurements (1.20 ± 0.07 vs 1.07 ± 0.08; p<0.05). CONCLUSIONS We conclude that holodiastolic reflux occurs in healthy patients. This physiological phenomenon merits further investigation and can help elucidate previous observations in different pathological conditions.