For many patients, the time spent meeting with their physician-the clinical encounter-is the most opportune moment for them to become engaged in their own health through the process of shared decision making. In the United States shared decision making is being promoted for its potential to improve the health of populations and individual patients, while also helping control care costs. In this overview we describe the three essential elements of shared decision making: recognizing and acknowledging that a decision is required; knowing and understanding the best available evidence; and incorporating the patient's values and preferences into the decision. To achieve the promise of shared decision making, more physicians need training in the approach, and more practices need to be reorganized around the principles of patient engagement. Additional research is also needed to identify the interventions that are most effective.