A systematic review of evidence for the efficacy of environment-based interventions on the affect, behavior, and performance of people with Alzheimer's disease and related dementias was conducted as part of the American Occupational Therapy Association's Evidence-Based Literature Review Project. Thirty-three reports met inclusion criteria. Results suggest that ambient music, aromatherapy, and Snoezelen are modestly effective in reducingagitation but do not consistently have long-term effects. Visually complex environments that give the illusion of barriers deter people from wandering to unsafe places but do not reduce the urge to wander. Evidence that bright light therapy can aid in regulating mood and the sleep-wake cycle and thus help people remain awake during the day is preliminary. Montessori-based programming can be useful in matching activities to the person's remaining skills. Further research is needed to evaluate the long-term effect, contraindications, and best dosages of these interventions.