To characterize asthma in the elderly, we compared asthma in patients aged over 70 without chronic obstructive pulmonary disease with that in patients in their twenties. In the elderly, 65.5% of the patients had developed asthma after they were fifty years old. The mean duration from onset of asthma was 21.4 years. Of cases in the elderly, 42.1% were severe, and 93.0% were chronic type. IgE was significantly lower in the elderly than in those in their twenties. Among the patients in their twenties, the severe cases had early onset and long duration. In the elderly, however, there were no correlations between severity and age at onset or duration. Severe cases in their twenties had more obstructive ventilatory dysfunction in the stable state than the mild cases. In the elderly, however, the mild cases had the same level of obstructive ventilatory dysfunction as the severe cases. The elderly patients who had more than twenty years duration had lower V50 and V25 than those who had a less than twenty-year history. Small airway obstruction was observed in long-standing cases. As asthma in the elderly causes obstructive ventilatory dysfunction in the stable state, elderly patients might easily develop respiratory failure, even during mild attacks.