Ten term infants who were exposed to maternal smoking during pregnancy and 10 age- and sex-matched control infants participated in the study. At the age of 48 hours (+/- 10), all infants underwent a 150- to 200-minute polygraphic study in a soundproof laboratory. Respiratory and heart rates, distribution of sleep states, and oxygen saturation were comparable in the two groups. The number and length of apneic events were similarly distributed in the two groups. The proportion of obstructive apneic events followed by arousal was significantly higher in the control group especially during quiet sleep (p = 0.001). It appears that exposure to smoking during pregnancy is associated with a higher arousal threshold in term infants. This finding could be of relevance in the assessment of maternal smoking as a risk factor for sudden infant death syndrome.