Juvenile delinquents in Japan are treated according to their legal status, degree of delinquent tendencies, and age. In most cases, the discovery and initial classification of a delinquent by the police is followed by referral to the public prosecutor, the family court, or the child guidance center. The range of treatment procedures poses an obstacle to the construction of consistent classification categories. The classification categories used by the juvenile police or the public prosecutor are based primarily on legal procedures, while the categories used by the family court and correctional institutions, including the juvenile classification home, are based on psychology and sociology. The classification of adult offenders is regulated by several ordinances and rules, with the most important being the Ordinance for Progressive Treatment of Prisoners and the Rules for the Prison Classification System. The former specifies that investigation and diagnosis for the classification of prisoners must be conducted on the basis of scientific knowledge. Prisoners are classified by sex, nationality, type of penalty, age, and term of imprisonment; degree of criminal tendency; and physical and mental disorders. Treatment classifications include specially required treatment, specially recommended treatment, and progressive grade. Probationers and parolees are classified according to the following categories of legal status: juvenile probationer, adult probationer, training school parolee, prison parolee, and guidance-home parolee. Probation and parole treatment classifications are also provided.