OBJECTIVES: This paper reports on the development of and psychometric validation of the Influenza Daily Disruption Questionnaire (IDDQ), a short new instrument to measure the disruptive effects of influenza on daily activities. METHODS: People with a previous influenza episode were recruited by newspaper advertisement to discuss the effects of influenza on their daily activities using a semi-structured interview technique. Each interview was transcribed, and a list of statements was generated via content analysis. A draft instrument was then developed for pilot testing. A cognitive debrief was included as part of the pilot test to gain a better understanding of patients' evaluation of the adequacy and relevance of the questionnaire. The final IDDQ was then produced. The IDDQ was administered in a clinical trial of influenza treatment. The psychometric properties of the instrument will be reported. RESULTS: Twelve respondents were interviewed for the drafting of the IDDQ, while another ten were used in the pilot testing of the draft eight-item instrument. On the basis of the pilot testing, one item was re-ordered, five items were slightly re-worded, and two items were left unchanged. The final version of the IDDQ has eight items, each relating to the effects of influenza on disruption of specific daily activities: self-care; shopping; housework; care for others; exercise; social life; hobbies, and work/school/college. Each item is scored on a five-point, Likert-type response scale, rated attitudinally from completely agree to completely disagree. CONCLUSION: This paper describes the successful development of a multi-item questionnaire to measure the effects of influenza on disruption of daily activities. Psychometric properties of the IDDQ will be presented.