• We evaluated 15 infants with laryngomalacia and 12 healthy Infants to determine their risk of hypoxia and hypercapnia as complications of partial upper airway obstruction. Transcutaneous carbon dioxide pressure and oxygen pressure were recorded continuously overnight with episodes of hypercapnia and/or hypoxia scored for frequency, duration, and relationship to activity. Episodes occurred in 12 infants with laryngomalacia and eight control infants. Infants with laryngomalacia had significantly more episodes. The greatest decrease in transcutaneous oxygen pressure was 29 mm Hg and increase in transcutaneous carbon dioxide pressure was 31 mm Hg, both occurring in infants with laryngomalacia. Three infants had prolonged episodes of hypoxia and hypercapnia. History or physical examination did not distinguish those infants with laryngomalacia who had hypercapnia and/or hypoxia from those without episodes. Two- to 15-month follow-ups in 13 infants with laryngomalacia revealed that symptoms were unchanged or improved. Twelve of these 13 infants had normal growth without developmental delay or other complications. These results demonstrate that episodes of hypoxia and hypercapnia occur more frequently in infants with laryngomalacia than in control Infants; however, their apparent risk for complications is low.