This paper presents an overview of literature regarding What Works" in criminal offender rehabilitation, with an emphasis on female offenders. Women in prison generally have another background and other criminogenic risk factors and general needs than males. These differences are important to consider when establishing an offender rehabilitation program that aims to be effective in reducing criminal behavior in female offenders. A discussion about the role of a prison is also presented, covering the tension between goals of both punishment and goals of rehabilitation within one institution. More specific, the role of the prison officers that implement most rehabilitation programs in Norwegian prisons today is discussed. The paper also presents a pilot study on a small Norwegian female offender sample to highlight the importance of a thorough structured and clinically based assessment. Such an assessment is needed to secure selection of responsive subjects to specific rehabilitation program. Because of the small sample findings cannot be generalized, but some general suggestions for future rehabilitation work are mentioned in the conclusion, amongst others: (1) counseling for the prison officers implementing the programs, (2) a total integration of all the What Works-principles, and (3) the use of adequate screening tools such as OASys.