Background: The role of IgE in COPD is currently unknown. An analysis of serum IgE in a large population of patients with COPD is lacking. Methods: The German COSYCONET cohort is a large, comprehensively characterised population of patients with COPD. Total IgE in serum was measured in 2280 patients of the cohort. Specific IgE against common aeroallergens was measured using the SX1 screening test. Results: The percentage of patients with elevated total IgE (> 100 IU/ml: 31.2 % of all patients), but not the percentage of patients with positive SX1 screening results, was higher than in general populations of European adults. Median total IgE was higher in men than in women with COPD. Men with at least one exacerbation in the last 12 months displayed higher total IgE (but not allergen-specific IgE) than men without exacerbations: this was not found in women (Fig. 1). A history of allergies, atopic diseases or a positive SX1 screening test were correlated with better lung function, better CO diffusing capacity and less emphysema, both in women and men. Conclusion: Higher total IgE was associated with exacerbations in men, but not in women with COPD. A history of allergies or presence of allergen-specific IgE were correlated with better lung function and less emphysema, independent of the gender. These data suggest a role for total IgE in COPD which is not explained by allergic sensitisations to common aeroallergens. Figure2