Objective: To develop a self-report measure for assessment of the stage of change in patients with osteoarthritis, in order to identify patients who would benefit from a self-management programme. Methods: According to the 'stages of change' model a questionnaire was developed with three groups of items corresponding to the precontemplation stage (Pre), the contemplation (Cont) and the action (Act) stage. Internal consistency and factor structure of this questionnaire were investigated by assessing Cronbach's alphas and by performing factor analysis. Subjects and setting: The questionnaire was offered to 273 patients who entered a randomized clinical trial on self-management in a general health care setting. Results: Factor analysis revealed that most items corresponded to the a priori described groups, while some items were not loading on the presumed factor. In each subgroup some items were deleted, resulting in a 15-item questionnaire. After this item reduction Cronbach's alphas were 0.72 (Pre), 0.76 (Cont) and 0.79 (Act) and all factor loadings were satisfactory (above 0.35). Classification revealed some differences between parts of the total group, for example in the proportion of patients in the preparation stage (recruited by general practitioner = 33.6%; advertisement = 49.2%). Conclusions: The Stages of Change Questionnaire in Osteoarthritis, a 15-item questionnaire to assess the 'stage of change' of a patient with osteoarthritis showed good internal consistency and adequate factor structure. These findings warrant further studies on validity and applicability in a clinical context.