Latin American and Spanish penal laws followed the same tradition until about 1921, when they went their separate ways. The codes were based on the principle that guilt is necessary for punishment and that prevention is the chief sentencing consideration. As in Germany, early 20th century reform legislation in Latin America was based on a compromise between traditionalists and reformers, while in Spain reform movements had little real effect on punishments or sentencing. Reforms affected the criminal codes of Argentina, Peru, Venezuela, Mexico, Uruguay, Columbia, Cuba, and Brazil. The new directions encouraged penalties according to offenders' dangerousness, consideration of offender types in sentencing, treatment of mentally incompetent or minor offenders through special measures, and responsibility of administrative authorities rather than the justice department for execution of penalties. Changes involved modernization of the penalty system, emphasis on special prevention in sentencing, introduction of probation and parole, adoption of special measures for recidivists as well as for juveniles and mental incompetents. In Spain, probation and parole were introduced, but dangerousness played almost no role in sentencing and the system of penalties was scarcely altered. Latin American reform movements after 1960 are characterized by scepticism towards criminal law based on special prevention alone and by emphasis on the role of guilt. The unification model propagated by the Model Criminal Code for Latin America (prepared 1963-1969) theoretically shifts emphasis from special prevention to individual responsibility. In practical terms, the model does not alter any of the already introduced special prevention measures and devotes most of its attention to redefining the guilt principle. The reform model embodied in the Argentinian proposals of 1974/75 focuses on the system of reaction of offenses. The model supports special prevention, uniform prison sentences, and resocialization measures. No progress is made in the area of sentencing. Measures for security and improvement are thoroughly redefined. Other changes affect dogma such as rules for prosecution of attempted offenses. Since 1972 even Spain has attempted to update its criminal law by decriminalizing certain offenses, among them adultery, use of birth control, political propaganda, and public gatherings. It is concluded that the course of Latin American reform is more rapid than that of either Germany or Spain. Spain continues to adhere to the principle of special prevention, while German criminal policy centers around the guilt principle. The future development of criminal law in Spanish-speaking countries will probably parallel the developments in Germany. Notes are supplied.