Decision aids for patients have recently been introduced in health care. A literature review was conducted to address the following research questions: 1) which types of decision aids have been developed?; 2) to what extent are they feasible, and acceptable to patients and health care providers?; 3) do decision aids affect the decision-making process and patients' outcomes? Thirty non-controlled (e.g., one-group-only designs) and controlled studies (e.g., randomized experimental designs) were identified. Decision aids were found to be feasible and acceptable to patients and to increase the agreement between patients' values and decisions and patients' knowledge. The effects of decision aids on decisions and on patients' outcomes, including decision uncertainty, satisfaction, and health, have rarely been addressed. When studied, the beneficial effects of decision aids on these outcomes appear to be rather modest. Implications for future development of decision aids and the design of studies are discussed.