Severe fatigue is a highly prevalent and bothersome symptom for patients with rheumatic diseases. Existing fatigue questionnaires have several disadvantages, for example containing generic fatigue items that might be confounded by disease specific disability, or being unidimensional, which is not in line with the patients´ experience of their fatigue symptoms. Therefore, we developed a multidimensional computerized adaptive test (CAT) which was based on the perspectives of patients with RA. In a CAT, items are successively selected from a large item bank (scaled using IRT), based on the patient’s previous answer. Measurement is thus tailored to the individual level, leading to greater measurement precision, with need of fewer items than traditional questionnaires. We studied the usability of CAT administration, demonstrated the working mechanisms of a computer adaptive test and validated the CAT.