We conducted a population-based survey of respiratory diseases and lung function in a New Mexico Hispanic community, and developed spirometric prediction equations based on data from 576 children and adults. Spirometric test procedures were followed as recommended by the American Thoracic Society. For children 6 through 18 yr of age, we used a logarithmic model to predict spirometric parameters. We used simple linear regression for adults 25 through 80 yr of age. On the basis of exploratory analyses, we excluded adult subjects who were obese, defined as a body mass index of 30 kg/m2 or greater. This report describes these regressions. We did not perform regression analysis for those subjects between 19 and 24 yr of age because of small numbers and the inappropriateness of grouping these subjects with older adults for regression analysis. As an alternative to a regression equation for this age group specifically, we propose linear interpolation between values obtained using prediction equations developed for children and for adults. Finally, we compared the percent predicted values obtained from our internal prediction equations with equations from other populations of white children and adults. In general, the comparison equations underestimated the percent predicted values in our population.