Background: Patient empowerment is viewed as a priority by policy makers, patients and practitioners worldwide. Although there are a number of measures available, none have been developed specifically for patients in the UK with long-term conditions. It is the aim of this study to report the development and preliminary validation of an empowerment instrument for patients with long-term conditions in primary care.Methods: The study involved three methods. Firstly, a systematic review was conducted to identify existing empowerment instruments, and to describe, compare and appraise their content and quality. The results supported the need for a new instrument. Item content of existing instruments helped support development of the new instrument. Secondly, empowerment was explored in patients with long-term conditions and primary care practitioners using qualitative methods, to explore its meaning and the factors that support or hinder empowerment. This led to the development of a conceptual model to support instrument development. Thirdly, a new instrument for measuring empowerment in patients with long-term conditions in primary care was developed. A cross-sectional survey of patients was conducted to collect preliminary data on acceptability, reliability and validity, using pre-specified hypotheses based on existing theoretical and empirical work. Results: Nine instruments meeting review inclusion criteria were identified. Only one instrument was developed to measure empowerment in long-term conditions in the context of primary care, and that was judged to be insufficient in terms of content and purpose. Five dimensions ('identity', 'knowledge and understanding', 'personal control', personal decision-making', and 'enabling other patients') of empowerment were identified through published literature and the qualitative work and incorporated into a preliminary version of the new instrument. A postal survey achieved 197 responses (response rate 33%). Almost half of the sample reported circulatory, diabetic or musculoskeletal conditions. Exploratory factor analysis suggested a three factor solution ('identity', 'knowledge and understanding' and 'enabling'). Two dimensions of empowerment ('identity' and 'enabling') and total empowerment showed acceptable levels of internal consistency. The measure showed relationships with external measures (including quality of chronic illness care, self-efficacy and educational qualifications) that were generally supportive of its construct validity.Conclusion: Initial analyses suggest that the new measure meets basic psychometric criteria and has potential for the measurement of patient empowerment in long-term conditions in primary care. The scale may have a role in research on quality of care for long-term conditions, and could function as a patient-reported outcome measure. However, further validation is required before more extensive use of the measure.