BACKGROUND: Comprehensive studies of the pathophysiologic characteristics of elderly asthma, including predominant site of disease, airway inflammation profiles, and airway hyperresponsiveness, are scarce despite their clinical importance. OBJECTIVE: To clarify the pathophysiologic characteristics of elderly patients with asthma. METHODS: Patients older than 65 years (elderly; n = 45) vs those no older than 65 years (nonelderly; n = 67) were retrospectively analyzed by spirometry, computed tomographic indices of large airway wall thickness and small airway involvement (air trapping), impulse oscillation measurements, exhaled nitric oxide levels, blood and induced sputum cell differentials, methacholine airway responsiveness, and total and specific serum IgE levels. RESULTS: Elderly patients with asthma had significantly lower values for forced expiration volume in 1 second, mid-forced expiratory flow (percentage predicted), and ratio of forced expiration volume in 1 second to forced vital capacity than nonelderly patients with asthma (median 81.2% vs 88.8%, P = .02; 50.9% vs 78.6%, P = .03; 0.72 vs 0.78, P = .001, respectively). In computed tomographic measurements, elderly patients with asthma had significantly greater airway wall thickening and air trapping than nonelderly patients. Impulse oscillation measurements indicated that elderly patients with asthma showed significantly greater resistance at 5 Hz (used as an index of total airway resistance), greater decrease in resistance from 5 to 20 Hz, a higher ratio of decrease in resistance from 5 to 20 Hz to resistance at 5 Hz, higher integrated area between 5 Hz and frequency of resonance, greater frequency of resonance, and lower reactance at a frequency of 5 Hz (potential markers of small airway disease) than nonelderly patients. There were no significant differences in blood or sputum cell differentials, exhaled nitric oxide, or methacholine airway responsiveness between the 2 groups. Total serum IgE levels and positive rates of specific IgE antibodies against several allergens were significantly lower in elderly than in nonelderly patients with asthma. CONCLUSION: Based on spirometric, computed tomographic, and impulse oscillation analyses, elderly patients with asthma have greater involvement of small and large airways than nonelderly patients with asthma.