Background: Normal reference values for pulse oximetry saturation (POS) have been established for healthy term newborns at sea level; however, normal values for POS have not been clearly defined for infants born at high altitudes. Objective: To determine reference values of POS during the 1st day of life in a sample of healthy term newborns born at >3500 m above sea level. Design/methods: A prospective cohort study in healthy term infants with a normal cardiopulmonary examination and an Apgar score of ≥8 was conducted in a community hospital in La Paz, Bolivia during August and September 2006. POS on the right hand, heart rate and respiratory rate were measured at 1, 12 and 24 hours after birth. Exclusion criteria were congenital malformations and having received supplemental oxygen during the 1st day of life. Results: 122 mothers and their infants were included. Mean (SD) birthweight was 3195 (416) g and 74.6% were born by vaginal delivery. Mean (SD) SPO2, at 1 hour in 84 infants was 88.7% (4.6) and this did not differ significantly during the 1st day of life [87.2% (3.9) at 12 hours (n=89), 88.2% (3.9) at 24 hours (n=93)]. There were no significant differences in SpO2 values at 1 hour between infants born by vaginal or caesarean delivery [88.6% (4.6) vs 88.9% (5.0), respectively; p=0.89]. Heart rate at the 1st hour ranged from 107 to 160 beats/min. Mean (SD) respiratory rate at the 1st hour was 52 (8) respirations/min. Conclusions: In healthy newborn infants born at >3500 m above sea level SPO2, the mean SPO2 values are in the high 80s, and these values persist during the 1st 24 hours of life. If these figures are confirmed by other large studies at similar altitude, they should be used as reference values in the medical care of neonates born at a similarly high altitude. © 2008 The Liverpool School of Tropical Medicine.