Extracorporeal membrane oxygenation (ECMO) in the newborn usually requires occlusion of a jugular vein, and frequently a carotid artery. The acute effects of jugular vein occlusion on cerebral blood flow characteristics have received little investigation. Six newborns (age range, 0 to 5 days; weight, 2.4 to 3.1 kg) were treated with venoarterial ECMO, with additional placement of a cephalic venous catheter, for meconium aspiration (4) or persistent fetal circulation (2). Doppler duplex ultrasound evaluation of blood flow velocity and resistive index (RI) in the right (RMCA) and left (LMCA) middle cerebral arteries was performed just before ECMO, immediately after ECMO onset, and at 8,24, and 48 hours of ECMO. Arterial Po2 was maintained at 80 to 120 mm Hg. Pco2 at 35 to 45 mm Hg. and mean arterial pressure at 50 to 60 mm Hg. Flow velocity was measured with the cephalic venous catheter both open and closed. Closure of the cephalic venous cannula resulted in an abrupt, significant reduction in RMCA flow velocity and a significant increase in RI at the onset of ECMO and at 8 hours of ECMO. Opening the cannula restored the velocity and RI to normal. LMCA velocity and RI did not change with closure of the cephalic venous cannula. All infants survived ECMO, and five of the six are normal neurologically at 1 year of age. These data show that right carotid ligation alone did not change cerebral arterial blood flow velocity, but the addition of venous occlusion significantly decreased RMCA flow velocity, which was alleviated by cephalic venous drainage. After 24 hours of ECMO, this effect disappeared. This suggests that cephalic venous drainage may help prevent the neurological complications of ECMO by maintaining normal cerebral blood flow.