Although many investigations have been conducted to characterize the pathogenesis of interstitial lung diseases, few examined the epidemiology of these disorders in a general population. The establishment of the registry represented the first step in a sequence of investigations designed to characterize the epidemiology of the interstitial lung diseases. The registry initially served a descriptive purpose; the incidence of the interstitial lung diseases was measured in a defined population. Subsequently the registry served as a mechanism for ascertaining cases for a case-control study. Finally, the registry provided population-based data for clinical purposes on presentation, physiology, and natural history of the interstitial lung diseases.