Some children with "aborted" sudden infant death syndrome (SIDS) and parents of SIDS victims have abnormal control of ventilation. Because apnea during sleep occurs in some children who go on to die of SIDS, and because the abnormality in ventilatory control may be familial, we examined breathing during sleep in parents of SIDS victims to determine whether breathing pattern abnormalities were common in them. We studied 12 patients (6 couples) of SIDS victims and 12 age-matched control parents with healthy children. We failed to demonstrate significant differences in the incidence of apneas or breathing pattern irregularities between the SIDS and control parents. However, 2 SIDS parents, 1 male and 1 female, had 44 and 31 apneic episodes, respectively, exceeding the number conventionally used to document excessive apneic episodes during sleep. Neither of these parents had the hundreds of apneic episodes usually seen in the sleep apnea syndrome. Although these 2 SIDS parents support the notion that a sleep breathing abnormality may exist in SIDS parents, most of the SIDS parents had normal breathing during sleep. Because the abnormalities in the two SIDS parents were minor, and because the remainder of the subjects were normal, we conclude that polysomnographic recordings fail to reveal a "marker" that might identify potential SIDS parents.