Objective: To determine the prevalence and relationship between apnea and gastroesophageal reflux (GER) among infants with apparent life-threatening events. Methods: We evaluated 67 infants of ages up to 6 months who had an idiopathic apparent life-threatening event as determined by polysomnography and pH monitoring. Results: No reflux (pH < 4 for more than 6 seconds) was evident in 32 infants. Fourteen others had such prolonged reflux that the relationship between apnea and reflux could not be evaluated. The 21 remaining infants who had episodes of apnea and reflux constituted the study group. In 81% of the apneic episodes, no relationship to GER was noted. Apnea preceded reflux in 93.6% of the episodes, and only 6.4% of the apneic episodes followed reflux. When apnea preceded reflux, the apnea was obstructive in 66.8% of episodes and mixed in 33.2%. Central apnea was not recorded preceding reflux. Conclusions: Episodes of apnea were seldom associated with GER. However, in those instances when apnea and reflux were associated, the predominant sequence of events was obstructive apnea and to a lesser extent mixed apnea followed by reflux. (J Pediatr 2000;137:321-6)