In order to investigate the effects of obstructive sleep apneas upon transcutaneous PO2 75 polysomnograms, recorded during night sessions in 25 control infants, 25 siblings, and 25 near miss for sudden infant death syndrome (SIDS) infants were studied. These observations were compared with the decreases in transcutaneous PO2 measured during central sleep apneas in the same infants. During a total of 707.6 hours of sleep, 33 obstructive apneas and 1,650 central apneas were recorded. Obstructive apneas were seen in three control infants (three episodes), one sibling (five episodes), and six near miss for SIDS infants (25 episodes). The obstructive apneas tended to be short (less than 10 seconds). Comparatively, the central apneas were equally distributed in the three groups of infants, and only the near miss children presented apneas that lasted as long as 19 seconds. The decrease in transcutaneous PO2 was proportional to the duration of both types of apnea, but for a given duration the decrease in transcutaneous PO2 was significantly greater for the obstructive apneas than for the central apneas (with a mean difference of 7.59 +/- 0.53% PO2. It is concluded that the hypoxic effects of the obstructive apneas might have important clinical implications in infants, such as the near miss for SIDS.