Correlations between relatives (N=1476 pairs) for lung function (FVC, FEV-3, FEV-1 and Peak Flow rate) and height were determined in an Aymara population residing at different altitudes in Chile. The correlations reflect a heritability of lung function (adjusted for age, sex and height) which is lower than that for height in this population. Few of the coefficients were significantly different from zero for the vital capacity (FVC), suggesting a high environmental determination of its variability. Heritabilities of Peak Flow rate and FEV-1 were higher (30-50 percent), while somewhat more than 50 percent of the variation in height in this population was attributable to genetic variation. Lung function correlations between relatives, one or both of whom had migrated to a different altitude, were lower than correlations between relatives who had not moved, suggesting environmental contributions to the correlations via common environment or genotype-environment interaction. This did not occur for height. A systematic reduction in the within-altitude heritability of Peak Flow rate occurred with increasing altitude. This is consistent with the influence of natural selection on this characteristic, although it is also consistent with selective migration of those unable to adapt.