Cerebral perfusion is reduced after prolonged periods of total circulatory arrest in infants. Methods of rewarming after arrest may modify the flow pattern of recovery, and a single report has suggested that using cold reperfusion to delay rewarming could mitigate abnormalities in cerebral blood flow. Cerebral perfusion was evaluated by transcranial Doppler sonography in 16 infants who required periods of total circulatory arrest of 35 minutes or more. In group A (n = 9) rewarming was begun immediately on reperfusion, whereas in group B (n = 7) a 10-minute period of cold reperfusion was instituted before rewarming was begun. The mean and end-diastolic flow velocities were measured before incision (baseline) and at 20, 45, and 90 minutes after conclusion of cardiopulmonary bypass. Mean arterial pressure, hematocrit value, and arterial carbon dioxide tension were controlled, with no significant differences between the two groups (p > 0.05). In group A, the mean cerebral blood flow velocity was below the baseline level at all three postbypass measurements (p < 0.001). In group B, however, mean velocity did not differ significantly from the baseline value (p > 0.05). Twenty minutes after bypass, 89% of the patients in group A had no diastolic Doppler signal, indicating absence of perfusion during diastole, compared with only 28% in group B (p = 0.02). These preliminary results suggest that a delay in rewarming on reperfusion may be beneficial in infants after circulatory arrest.