Objective: To compare the blood flow velocities of superior mesenteric artery (SMA) before versus after clarithromycin treatment for feeding intolerance in very low-birth weight infants.Methods: A prospective study was conducted in a group of infant <1500g with feeding intolerance who received clarithromycin 7.5mg/kg/dose bid. Before and at the third day of the clarithromycin therapy, SMA blood flow velocity was measured with Doppler ultrasound.Results: SMA peak systolic velocity (PSV) and mean systolic velocity (MV) on the third day of the treatment was found significantly higher than the initial measurement (p=0.013 and p=0.027, respectively). End diastolic velocity of the SMA did not change with clarithromycin therapy (p=0.113). There were no significant changes about pulsatility and resistive index of SMA with regard to clarithromycin therapy.Conclusion: Clarithromycin effects the splanchnic circulation. The rise in PSV and MV in SMA is remarkable. These results suggest that the splanchnic blood flow increases significantly after clarithromycin usage.