Introduction/Objective: To consider the criteria against which the effectiveness, cost effectiveness and appropriateness of interventions to promote patient involvement in health care decision making might be judged.

Methods: A critical discussion, drawing on existing theoretical and empirical work in several disciplines. For each outcome area identified, key issues in conceptualization and measurement are considered.

Results: Interventions to inform patients about health care options and involve them in clinical decisions may have a variety of aims and a complex range of clinical, social and economic consequences. The outcome areas (including health care processes) identified include: knowledge and understanding; beliefs and expectations; professional-patient relationships; decision making processes and decisions made; health care delivery and uptake; health status; and satisfaction. The assessment of outcomes from the perspectives of health professionals, patients and third parties, and the consideration of effects at individual, organisational and broader social levels, will be important for a multi-layered understanding. Although some measures exist for the outcome areas identified, few were developed specifically to evaluate interventions to involve patients in decisions about their care, and they may be of limited use in these contexts.

Discussion: The development and validation of appropriate outcome measures to evaluate interventions to promote patient involvement in clinical decision making should be a research priority in the current climate of enthusiasm for informed patient choice. Careful consideration should be given to existing bodies of theoretical and empirical work from a range of academic and clinical disciplines.