Cerebral blood flow velocities (CBFV) were measured by the pulsed Doppler method in 41 infants of smoking mothers and in 59 apparently healthy control infants. Although gestational age, birth weight, and systolic blood pressure were lower in infants exposed to tobacco smoke prenatally, systolic (65 +/- 11 vs. 47 +/- 12 cm/s, mean +/- SD; P < 0.001), mean (36 +/- 6 vs. 25 +/- 6 cm/s; P < 0.001), and diastolic (17 +/- 4 vs 13 +/- 4 cm/s; P < 0.001) CBFVs in the anterior cerebral artery were significantly higher when compared to control infants. Similar differences were seen in the internal carotid and in the basilar arteries. Multiple regression analysis did not reveal differences other than maternal smoking to explain these observations. We conclude that prenatal tobacco smoke exposure is related to increased CBFVs in newborn infants. Further studies should determine whether this relation is not only statistical but causal and whether increased CBFVs are an indicator of prolonged effects of prenatal tobacco smoke exposure.