There are few data in the literature related to polysomnography in infants in altitudes from 2,200 m to 2,800 m.The main objective of this investigation was to describe oxygen saturation (SpO 2 ) levels during sleep in infants aged between 1 and 4 months living at an altitude of 2,560 m.The secondary objectives were the description of periodic breathing (PB) and apnea indexes.Polysomnography was performed in 35 healthy infants 1-4 months in Cuenca (Ecuador) at 2,560 m.The median for SpO 2 was 92% and 4.9% for PB.The median for the central apnea index was 23.7/hour and 15.4/hour when related to PB.No correlation was found between PB and SpO 2 .Conclusion: SpO 2 was lower than the values at sea level and PB and central apnea indexwere higher.When apneas associated with PB were not considered, the central apnea indexwas similar to that found at sea level.