The National Center for Complementary and Alternative Medicine defines meditation as a "mind-body" method. This category of complementary and alternative medicine includes interventions that employ a variety of techniques that facilitate the mind's capacity to affect bodily function and symptoms. In meditation, a person learns to focus attention. Some forms of meditation instruct the student to become mindful of thoughts, feelings, and sensations, and to observe them in a nonjudgmental way. Many believe this practice evokes a state of greater calmness, physical relaxation, and psychological balance. Many people use meditation to treat stress and stress-related conditions, as well as to promote general health. A number of hospitals and programs offer courses in meditation to patients seeking alternative or additional methods to relieve symptoms or to promote health. Meditation training programs vary in several ways, including the emphasis on religion or spirituality, the type of mental activity promoted, the nature and amount of training, the use of an instructor, and the qualifications of an instructor, which may all affect the level and nature of the meditative skills learned. Some meditative techniques are integrated into a broader alternative approach that includes dietary and/or movement therapies (e.g., ayurveda or yoga). Researchers have categorized meditative techniques as emphasizing "mindfulness," "concentration," and "automatic self-transcendence." Popular techniques such as transcendental meditation (TM) emphasize the use of a mantra in such a way that one "transcends" to an effortless state where there is no focused attention. Other popular techniques, such as mindfulness-based stress reduction (MBSR), are classified as "mindfulness" and emphasize training in present-focused awareness. Uncertainty remains about the extent to which these distinctions actually influence psychosocial stress outcomes. Researchers have postulated that meditation programs may affect a range of outcomes related to psychological stress and well-being. The objectives of this systematic review are to evaluate the effects of meditation programs on affect, attention, and health-related behaviors affected by stress, pain, and weight among people with a medical or psychiatric condition in RCTs with appropriate comparators. This report reviews the efficacy of meditation programs on psychological stress and well-being among those with a clinical condition. The Key Questions are as follows: Key Question 1. What are the efficacy and harms of meditation programs on negative affect (e.g., anxiety, stress) and positive affect (e.g., well-being) among those with a clinical condition (medical or psychiatric)? Key Question 2. What are the efficacy and harms of meditation programs on attention among those with a clinical condition (medical or psychiatric)? Key Question 3. What are the efficacy and harms of meditation programs on health-related behaviors affected by stress, specifically substance use, sleep, and eating, among those with a clinical condition (medical or psychiatric)? Key Question 4. What are the efficacy and harms of meditation programs on pain and weight among those with a clinical condition (medical or psychiatric)?