To determine if a familial abnormality in the control of breathing might explain the reasons for the sudden infant death syndrome (SIDS), three groups of parents were studied. The first (N = 8 sets of parents) had one infant die of SIDS (one SIDS), whereas the second (N = 6) had a SIDS victim plus a second child with a "near-miss" occurrence (two SIDS). When compared to the third group (controls), these parents demonstrated no abnormality in the ventilatory response to hypoxia or hypercapnia. Similarly, they had normal respiratory frequency, tidal volume, inspiratory time, and arterial blood gas tensions. We conclude that a familial abnormality in breathing control measured during wakefulness is not the basis for SIDS.