This chapter discusses the theories of change that relate to how offenders can be assisted to change their offending through treatment. It considers how to promote motivation to engage in treatment and change behaviour. Andrews and Bonta distilled and refined their principles of effective offender treatment into what is known as the Risk-Need-Responsivity (RNR) model. Theories of motivation for treatment and behaviour change may be described in three main approaches: matching intervention with stage of change; readiness to change; and goal perspectives. The Transtheoretical Model of Change was described first by Prochaska and DiClemente in relation to smoking cessation and was subsequently widely applied in addiction treatment. Ward and colleagues have proposed the Good Lives model (GLM) of offender rehabilitation, which focuses on helping offenders attain satisfaction in a range of life areas rather than focusing purely on reducing risk.