A 24 hour pH-metry was performed in children younger than 3 months divided in 4 groups: group 1: 37 infants who presented an apparent life-threatening event (ALTE), group 2: 45 infants with an ALTE and chronic digestive symptoms (recurrent vomiting), group 3: 33 infants with digestive symptoms only, group 4: 32 sudden infant death syndrome (SIDS) siblings. The percent duration of oesophageal pH below 4 (% pH < 4) was measured during 24 hours and 12 nocturnal hours (8 PM-8 AM). In addition the mean duration of nocturnal episodes of reflux (MDNR) was calculated (duration of pH < 4 per 12 nocturnal hours/number of reflux episodes). No significant difference was found in the 4 groups for % pH < 4. Nocturnal reflux was present in all groups (40% in group 1, 55% in group 2, 49% in group 3 and 63% in group 4). The MDNR was higher in group 1 (12.3 +/- 7.8 min) vs group 2 (6.8 +/- 5.1 min) and group 3 (6.7 +/- 3.2 min) (P < 0.05). High MDNR did not appear to be related to an history of ALTE since the MDNR in group 2 was identical to group 3. Nocturnal pH metry profile failed to show a relationship between gastro-oesophageal reflux and ALTE.