Airways remodelling is a feature of longstanding asthma, but may differ in persons with allergic and nonallergic asthma. To assess airways remodelling indirectly, we compared permanent CT-scan abnormalities in 70 subjects with allergic (median age: 30 yr) and 56 with nonallergic asthma (median age: 54.5 yr) who had had asthma of similar duration. None of the subjects were smokers. Asthma severity was assessed by Aas score and FEV1. Permanent high-resolution computed tomographic (HR-CT) scan abnormalities were characterized. In comparison with allergic asthmatic subjects, those with nonallergic asthma had a significantly greater frequency of cylindric (p < 0.0007, Mann-Whitney U test) and varicose (p < 0.004) bronchiectasis, emphysema (p < 0.0003), bronchial recruitment (p < 0.0001), and sequellar linear shadows (p < 0.0001). There was a significant correlation between Aas score and emphysema (p < 0.0001 for nonallergic and p < 0.0005 for allergic asthma; Kendall's test method) or Aas score and sequellar linear shadows (p < 0.007, nonallergic asthma). There was a significant increase in the extent of permanent abnormalities with increasing severity and duration of asthma in both groups. Patients with brittle asthma had few permanent abnormalities. This study confirms that after a similar course of the disease, patients with nonallergic asthma have a more extensive remodelling of the airways than those with allergic asthma.