Oscillatory patterns in ventilation have been seen in term and premature infants and are indicative of the stability of the respiratory blood gas feedback control system. Apneas are related to these patterns and apnea duration is correlated with pattern characteristics. In our study breathing patterns were analyzed in recordings from 10 term infants who subsequently died of sudden infant death syndrome (SIDS) and 10 control infants matched for birth wt, gestational age, and postnatal age. Subjects were drawn from a prospectively studied population of 9856 infants. Breath-by-breath minute ventilation was estimated in each of these 24-h recordings and oscillatory patterns were detected using a comb of digital bandpass filters. Confidence limits on the filter output and a bad data flag for rejection of data during gross body movements or crying insured that only significant patterns in ventilation were evaluated. Pattern prevalence and amplitude were compared in three frequency regimes: 6- to 87-s cycle times, 6- to 28-s cycle times, and 28- to 87-s cycle times. There was no significant difference between the SIDS and the control infants in any of these pattern comparisons (paired t and Wilcoxon paired rank sum tests, p less than 0.05). In light of the normal breathing patterns found in the SIDS infants, it is unlikely that susceptibility to SIDS is distinguished, at the time of these recordings, by instability of the respiratory blood gas feedback control system.