Duplex ultrasound is established for the assessment of mesenteric ischemia but potential influences of breathing on mesenteric arterial blood velocity have not been investigated so far. In 100 patients without abdominal diseases (39 men; age 59.4 ± 18.0 years), peak systolic (PSV), end diastolic velocity (EDV) and resistance index (RI) were assessed in the celiac trunk (CT) and the superior mesenteric artery (SMA) by Doppler ultrasound during expiration and deep inspiration. Expiratory PSVs in the CT and the SMA (153.4 ± 42.5 and 145.3 ± 39.5 cm/s) were significantly higher than inspiratory velocities (135.4 ± 36.8 and 131.9 ± 42.2 cm/s, p < 0.0001 and p = 0.0002), with expiratory PSVs exceeding inspiratory PSVs in more than 75% of patients. The mean percentage of PSV-variation was 21.5% ± 15.3% and 24.6% ± 19.1%, respectively. The study demonstrates that breathing may exert considerable periodic effects on splanchnic arterial hemodynamics. We, therefore, recommend that to prevent an underestimation of arterial stenosis, mesenteric Doppler ultrasound should be performed during expiration.