Among 857 infants admitted between 1977 and 1984 for a life-threatening apnoeic event a definite pathologic condition was found in 576 (66%). In 32 (6.5%) of the latter the polysomnogram was abnormal. The major clinical diagnostic categories were, with decreasing frequency: digestive (n = 263), vasovagal (n = 95), neurological (n = 78), respiratory obstructions (n = 33), and respiratory infections (n = 27); miscellaneous causes were found in 80 infants. No obvious cause could be traced in the remaining 281 infants. According to those caring for them the episode was severe in 77 (27%) of these infants, 57 (74%) of which had an abnormal polysomnogram, and minor in 204 (73%), 36 (18%) of which had an abnormal sleep study. Home monitoring was performed for 145 patients: all those with an abnormal polysomnogram and the 20 infants with an unexplained severe episode associated with a normal sleep study. We conclude from our experience that when an infant is referred for an acute event suggesting near-miss sudden infant death syndrome (SIDS), a large array of diagnoses can be found and that an electric monitoring device will ultimately be advocated for only 17% of all infants presented, but for all those with an unexplained severe episode, irrespective of the results of the sleep study.