A systematic review of the literature examined intervention studies designed to increase patients' participation in medical consultations. Twenty-five papers describing twenty studies met the inclusion criteria. About half of the intervention studies were randomised placebo controlled experimental designs. The studies were predominantly conducted in outpatient or primary care settings, with 50% of the interventions presented in a written form. Overall, half of the interventions resulted in increased patient participation, with slightly more significant results found for bids for clarification than question-asking. However, of the 10 written interventions only two reported a significant increase in question-asking. Patient satisfaction was the most commonly measured outcome, but few significant improvements were found. However, there were significant improvements in other outcomes, including perceptions of control over health, preferences for an active role in health care, recall of information, adherence to recommendations, attendance, and clinical outcomes. Few studies examined the links between patient characteristics and the success of the interventions. Future research needs to establish which forms of intervention are most effective and practical, for which groups of patients.