Objective: Rheumatoid arthritis (RA) patients experience fatigue as a multidimensional symptom. The aim of the present study was to use health professionals and patients alike to identify which dimensions of fatigue should be measured in RA. Methods: Twelve fatigue dimensions were constructed, based on items from traditional questionnaires and items generated from interviews. Health professionals and patients evaluated these dimensions, related to an initial pool of 294 items, in a Delphi procedure. Dimensions were selected if rated important by at least 80% of the participants. Results: Ten rheumatologists, 20 nurses and 15 patients participated. All fatigue dimensions were selected directly (severity, frequency, duration, changes in fatigue, perceived causes of fatigue, energy, sleep/rest, body feeling, cognition/concentration, coping, negative emotions/mood and consequences). No additional dimensions emerged from participants' comments and suggestions. Conclusions: This study revealed 12 fatigue dimensions. This underlines the multidimensionality of fatigue in RA and the need for comprehensive measurement.