We observed an increased incidence of gastroesophageal reflux (GER) in a group of preterm infants. Seventy-five infants (birth weight 1117 +/- 242 gm, gestational age 30 +/- 3 weeks) were tested within 1 week before hospital discharge (37 to 38 weeks postconceptional age). All of the infants had a two-channel pneumocardiogram and a 1-hour esophageal pH study (Tuttle test). Home monitors were used for all infants after hospital discharge and their use was maintained until standard discontinuation criteria were achieved. The Tuttle test was abnormal in 47 (63%) of the infants. Of the 47 infants with GER, 22 (47%) had evidence of obstructive apnea during the periods of reflux and 32 (68%) had an abnormal PCG result. Thirty-eight (81%) of the infants with GER had episodes of either obstructive or central apnea. The diagnosis of GER is important in premature infants because of the high association with recurrent or obstructive apnea.