Doppler blood flow velocity of the superior mesenteric artery was measured preprandially and postprandially in 12 term neonates during phototherapy and 4 hours after discontinuation of this therapy. The postprandial increase in blood flow velocity was significantly less during than after phototherapy. We suggest that the phototherapy-induced peripheral vasodilation may be responsible for diverting blood from the intestines and limiting the normal neonatal postprandial response.