OBJECTIVES: This paper reports on the psychometric properties and further development of the Influenza Daily Disruption Questionnaire (IDDQ). Each item of the IDDQ is answered by indicating degree of agreement using a five point response scale (completely agree, agree, neither agree nor disagree, disagree, completely disagree) with eight sentences describing the effects of influenza on disruption of daily activities. METHODS: The IDDQ was administered daily in a clinical trial assessing influenza treatment. IDDQ psychometric properties were assessed by examining item response spreads, internal consistency, and factor analysis. IDDQ scores were examined by age, gender, and body mass index (BMI) and correlated with patient-reported physical symptoms (nasal congestion, sore throat, cough, aches and pains, fatigue, headache, chills/sweats). Item-response models were also applied. RESULTS: Factor analysis supported IDDQ unidimensionality; at each day only one component explaining around 90% of total variance was extracted. IDDQ construct validity was supported by significant correlation coefficients between most IDDQ items including the IDDQ total score and all seven symptoms, in terms of both day-to-day and AUC scores. While half of the items had well-distributed response ranges, for others patients used mainly one end of the scale. These same items were the least internally consistent and on Rasch analysis most likely to have reversed thresholds related to the mid-point response 'neither agree nor disagree' (individual item fit p<0.01). In general, there was only a low probability of subjects choosing the mid-point response option. The mid-point response was therefore dropped in a revised IDDQ which has a four-point response scale (completely agree, agree, disagree, completely disagree). CONCLUSIONS: The revised IDDQ with a four-point response scale has acceptable psychometric properties. Further use of the revised IDDQ is recommended, especially in community-based epidemiological studies which may capture a broader spectrum of severity of influenza that usually seen in clinical studies.