OBJECTIVES: Bipolar disorder, as well as some of the pharmacological agents used to treat it, often impairs patients' ability to function on a day-to-day basis. The goal of the present study was to develop a sensitive, psychometrically sound self-report instrument that would help to identify treatments effective in maximizing the functional status of bipolar patients. METHODS: Through consultation with key opinion leaders, literature review, and individual in-depth interviews with bipolar patients, the team developed a questionnaire using 50 items to address the following domains: cognitive functioning, sleep, role functioning, emotional functioning, energy/vitality, social functioning, personal management, and sexual functioning. The draft questionnaire was then tested and revised through 2 iterative sets of cognitive interviews with 19 additional patients in multiple locations. RESULTS: In general, the pretest participants deemed the set of constructs addressed in the questionnaire to be both comprehensive and representative of their daily functioning. They also reported that the final set of items was easy to comprehend and to fill in, noting that the 7-point Likert-type response scale seemed optimal; the points on the scale appeared to represent the full spectrum of answer choices, yet participants could easily distinguish between the options. Cognitive testing also resulted in the elimination of 17 items, which were either deemed inessential to the measurement of functional status, applicable only to a subset of patients (eg, family responsibilities), or too similar in content to other items. CONCLUSIONS: The resulting questionnaire addresses all constructs considered central to the functional status of patients with bipolar disorder, with 33 items that are phrased to facilitate patient comprehension and completion. A multisite, 600-patient validation study is currently under way to evaluate the psychometric properties of this instrument.