This TIP is based on a fundamental rethinking of the concept of motivation. Motivation is not seen as static but as dynamic. It is redefined here as purposeful, intentional, and positive-directed toward the best interests of the self. Specifically, motivation is considered to be related to the probability that a person will enter into, continue, and adhere to a specific change strategy. This TIP shows how substance abuse treatment staff can influence change by developing a therapeutic relationship that respects and builds on the client's autonomy and, at the same time, makes the treatment clinician a partner in the change process. The TIP also describes different motivational interventions that can be used at all stages of the change process, from precontemplation and preparation to action and maintenance, and informs readers of the research, results, tools, and assessment instruments related to enhancing motivation.