OBJECTIVES: To evaluate the psychometric characteristics of the Acute Bronchitis Symptom Severity (ABSS) Scale, a new 7-item bronchitis-specific instrument designed to measure outcomes in chronic bronchitis (CB) patients. METHODS: Data were obtained from the screening phase of an international clinical trial comparing the effectiveness of moxifloxacin to a standard oral antibiotic treatment in treating an acute exacerbation of CB. Subjects had a primary diagnosis of CB (having presented with = 2 episodes of exacerbation in the preceding year, FEV1 < 85% of predicted value, and history of smoking), but were not currently experiencing an acute exacerbation. Patients from 19 countries completed the ABSS (14 languages) for 8 consecutive evenings. Psychometric characteristics evaluated were item performance, internal consistency reliability (Cronbach's alpha), day-to-day reproducibility (intraclass correlation coefficient (ICC)), construct validity (based on correlation with the St. George's Respiratory Questionnaire (SGRQ)), and discriminant validity (based on stratification by pulmonary function (FEV1 % predicted)). RESULTS: 1935 patients were enrolled. Mean age was 63.4 years (± 9.7) and 68% were male. Mean CB duration was 11.7 (± 9.6) years, with a mean of 2.9 (± 1.3) acute exacerbations in the prior year. The ABSS showed evidence of good internal consistency reliability (Cronbach's alpha=0.83), reproducibility (ICC=0.67), and construct validity (correlation with total SGRQ: r=0.54, p<0.05). Among the subscales, correlation was highest with the SGRQ Symptom subscale (r=0.53, p<0.05), as expected. Discriminant validity was generally good based on score spread across pulmonary function categories (mean score=0.99 for mild, 1.22 for moderate, and 1.38 for severe impairment). Psychometric results were supported across the language versions. CONCLUSIONS: The ABSS is a valid, reliable scale for evaluating the symptoms associated with CB during the stable phase away from an acute episode.