Respiratory distress, apnea, and chronic pulmonary disease since birth were identified in 14 infants who also had symptomatic gastroesophageal reflux. Birth weights varied from 760 to 4,540 gm. All infants had radiographic changes similar to those in bronchopulmonary dysplasia. Cessation of apnea and improvement of pulmonary disease occurred only after medical (8) or surgical (6) control of gastroesophageal reflux. Simultaneous tracings of esophageal pH, heart rate, impedance pneumography, and nasal air flow in five infants demonstrated that reflux preceded apnea. Apnea could be induced by instillation of dilute acid, but not water or formula, into the esophagus. Prolonged monitoring of esophageal pH more than two hours after feeding in 14 other infants less than 6 weeks of age (birth weight 780 to 3,350 gm) without a history of recent vomiting indicated that reflux was not greater than in normal older children.