From 1977 to 1981, 500 infants had been referred to evaluate their risk for the sudden infant death syndrome (SIDS). These included 186 infants who had presented an event (prolonged apnea, hypotonia, pallor or cyanosis) initiated while asleep, 133 siblings and 181 "controls". All-night polygraphic recordings were performed in all infants, and if indicated by the history of the infants, complementary clinical investigations were done. These procedures led to the identification of 50 infants considered at risk for SIDS (10% of all referrals): 30 near-misses for SIDS, 10 siblings and 10 infants with a minor incident during sleep but with abnormal polygraphic recordings. These 50 infants (group I) were monitored at home during sleep with the help of a cardiac and respiratory monitor. Eight infants not considered at risk were monitored similarly at the request of their parents (group II). Forty of the 50 infants in group I presented with repetitive sleep apneas and bradycardias, and required stimulation by their parents to regain normal cardiorespiratory rhythm. Twelve had to be resuscitated at least once for a life-threatening event. None of the infants in group II showed alarms during sleep. Monitoring could be discontinued after a mean length of 7.2 months for the infants in group I, 4.1 months in group II. It is concluded that if identified in time through adequate investigations, some infants may be protected against SIDS through home monitoring. This approach requires expensive and well trained teams, ready, at any time, to cope with the problems that may arise in the homes of the monitored infants.