Twenty-four infants, 32 weeks of gestation or less, were studied with continuous recording of amplitude integrated electroencephalogram (aEEG) and repeated Doppler ultrasound determination of the mean blood flow velocity in the internal carotid artery (cMFV). The recording was started after the initiation of mechanical ventilation for respiratory distress. Of twelve infants receiving blood or albumin transfusion to expand the intravascular volume and in whom adequate data were available, both mean arterial blood pressure and cMFV increased in eight, and cMFV but not blood pressure in further two. In the present circumstances we consider the cMFV increases to represent true increases in cerebral blood flow. aEEG burst rate increased distinctly in five of the twelve infants during or immediately following transfusion, but did only approach the level of the four non-transfused infants after several hours, indicating a dysfunction of neural tissue not readily reversible by improved blood flow.