The U.N. has already organized five congresses on the prevention of crime and the treatment of offenders: Geneva, Switzerland (1955); London, England (1960); Stockholm, Sweden (1965); Kyoto, Japan (1970); and Geneva (1975). The next one will take place in Sydney, Australia, in 1980. The agenda of the 1955 Geneva congress covered standard minimum rules for the treatment of prisoners; selection, training, and status of prison personnel; open penal and correctional institutions; prison labor; and the prevention of juvenile delinquency. The 1960 congress focused on new forms of juvenile delinquency, their origin, prevention, and treatment; special police services for the prevention of juvenile delinquency; prevention of types of criminality resulting from social changes and accompanying economic development in less developed countries; short-term imprisonment; the integration of prison labor with the national economy; prerelease treatment; and assistance to dependents of prisoners. Items on the agenda of the 1965 congress included social change and criminality; social forces and the prevention of crime; community preventive action; measures to combat recidivism; probation, especially adult probation; and treatment measures for young adults. The next congress, in 1970, discussed social defense policies in relation to development planning, participation of the public in the prevention and control of crime and delinquency, and research for policy development in social defense. Criminal legislation, emerging roles of the police, and changes in forms and dimensions of criminality were discussed at the 1975 meeting. Comments and footnotes are included.