The Latin American population is widely diverse in race and ethnicity; many individuals identified as mixed ethnicity makes selection of spirometry reference equations difficult. Additionally, 17% of Latin Americans live above 2500 meters above sea level which may influence lung development during childhood. Our aim was to investigate the role of altitude on spirometry, and whether a race-neutral reference equation (GLI-Global) fits subjects living at different altitudes. Methods: Data from 9 cities, classified as low (?1500 m), moderate (1500-2500 m), and high (? 2500 m) altitude were collected. Z-scores for FEV1, FVC and FEV1/FVC were expressed using GLI-Global equations. Mixed-effects regression models were used to describe the differences in lung function across altitude adjusted for height, weight, BMI, sex, and age. Results: 4480 ?healthy? individuals (3 to 94 years) were included. Average FEV/FVC z-score did not differ between the three altitude groups, whereas at higher altitudes, GLI-Global underestimates FEV1 and FVC (Fig 1). Adjusted for other factors, altitude explained up to 32% of the variability in spirometry.  Conclusion: Individuals at high altitude are likely to have their FEV1 and FVC underestimated using GLI-Global reference equations. Further work is needed to elucidate why people living at altitude have larger than predicted lung function.