As of mid-2004, American prisons and jails housed 2.1 million inmates, or one out of every 138 people in the United States. When these prisoners are released, the majority will be arrested for a felony or serious misdemeanor within three years. Clearly, the prison system fails to rehabilitate many offenders. But of the various methods proposed for rehabilitation, which have proved most successful, and which treatments look most promising for the future? This discussion of the treatment of criminal offenders explores the various trends in public opinion that influence crime prevention efforts, create public policy and reform criminal law. The work discusses three core issues in the study of punishment: the role of free will and determination; the search for the root cause or causes of crime; and the effects of studying crimes versus studying criminals. It provides a brief history of the American prison, highlighting the continuous debate regarding the rehabilitation and punishment of criminals. Additional topics include the history of biologically and psychologically based treatments; the principles of effective intervention; and what lies ahead in the 21st century.