Attention has increasingly been given to "greening" the environment, that is, to engaging in environmentally responsible behavior. Applied to hospitals, greening is collective interdisciplinary organizational behavior that reduces environmental hazards and overconsumption. An environmental crisis in hospitals is described. A number of individual and group psychological phenomena are detailed to explain the current absence of widespread greening in hospitals. Social and environmental psychology concepts for behavior change are combined to provide a model consisting of hospital administration and staff interventions to green this setting. Successful examples of these interventions are provided.