Résumé : The sudden and unexplained death of sleeping infants aged less than 1 year, the sudden infant death syndrome (SIDS), is still the principal cause of postneonatal mortality in many industrialized countries. Since initiation of education and information campaigns to inform the public on preventable risk factors, SIDS incidence has dropped significantly in most countries. Questions have, however, been raised on the physiological mechanisms underlying the environmental factors increasing the risk for SIDS. From the scientific literature, it appears that various mechanisms responsible for the control of respiratory, cardiac, thermoregulation, neurovegetative, and waking systems could be impaired before or after birth of future victims of SIDS. To understand how various factors contribute to SIDS deaths, we studied the characteristics of sleeping infants in two different populations, in future SIDS victims and in healthy infants exposed to conditions known to favor SIDS. This paper will review research carried out by our laboratory over the past 20 years.