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.