All subjects participating in the Normative Aging Study were recruited for the study at the time of their next scheduled examination. Twenty-four hour urinary excretion of free cortisol, morning serum cortisol concentration, and pre- and post-bronchodilator spirometric indices were measured. For the 700 subjects who were recruited during years one and two of the study, these measurements were repeated when subjects returned for their next triennial examination in years four and five of the study. Respiratory illness and smoking questionnaire data, total and differential leukocyte counts, and methacholine inhalation challenge test data were also available at both time points. The specific aims of the study were to examine: (1) the cross-sectional relationship between level of pulmonary function and both morning serum cortisol concentration and 24-hour urinary free cortisol excretion; (2) the relationship between the rate of decline of pulmonary function during the follow-up interval and these measurements of cortisol concentration and excretion; (3) whether these relationships were modified by smoking history, blood total leukocyte count, methacholine airway responsiveness, or other characteristics; and (4) the stability over time of serum cortisol concentration and urinary cortisol excretion in this aging population.