UP TO THE 18TH CENTURY, PRISONS IN MEXICO WERE EXCLUSIVELY OF THE PREVENTIVE TYPE. AZTEC AND MAYAN CULTURES DEVELOPED PRISONS FOR PREVENTIVE CUSTODY, I. E., AS PLACES WHERE OFFENDERS ANTICIPATED A FATE SUCH AS TORTURE OR DEATH. THERE WERE NO REHABILITATIVE CONCEPTS IN THESE AND OTHER CULTURES AND NO IDEA OF READAPTATION AND REINTEGRATION INTO SOCIETY. THE COLONIZATION OF THE NORTH AMERICAN CONTINENT BY SPAIN TRANSPLANTED ALL OF SPANISH PENAL LAW AND THUS PRACTICALLY ABOLISHED TRIBAL LAW. PENAL LAW IN MEXICO PERSISTED UNTIL 1871 WHEN COMPLETE REFORM WAS INITIATED BY THE GOVERNMENT. FOR THE FIRST TIME IN THE COUNTRY'S HISTORY, AFTER THE FORMULATION OF VARIOUS ISOLATED PENAL CODES, MEXICO ESTABLISHED A TRUE SYSTEM FOR THE EXECUTION OF SENTENCES THAT CONTAINED ALL NECESSARY ELEMENTS (LAW, APPROPRIATE INSTALLATIONS, PERSONNEL SELECTION AND TRAINING, SYSTEMATIZATION, USE OF DISCIPLINE, PARALLEL TREATMENT OF THE COMMUNITY THAT PRODUCED THE DELINQUENT, POSTINSTITUTIONAL ASSISTANCE, AND ASSISTANCE TO VICTIMS OF OFFENSES). MINIMUM STANDARDS ESTABLISHED BY THE UNITED NATIONS WERE APPLIED TO PREVENT CRIME AND TO TREAT OFFENDERS. THE REFORM INITIATED IN 1966 ENCOMPASSED THE ESTABLISHMENT OF A COMPLETE LEGAL CONTEXT THAT AMENDED THE CONSTITUTION, THE ENACTMENT OF LAW FOR THE EXECUTION OF FREEDOM-RESTRICTING SENTENCES, AND REGULATIONS FOR MODEL PRISONS AND PROCEDURES TO BE FOLLOWED WITH REGARD FREED CONVICTS. TOTAL PRISON REFORM ON THE FEDERAL LEVEL IN MEXICO WAS CARRIED OUT IN 1971. THE GENERAL MEXICAN APPROACH TO PREVENTING CRIME AND TREATING OFFENDERS IS DIRECTED ALONG THE LINES OF HUMANITARIANISM; THE ELIMINATION OF THE DEATH SENTENCE; AND THE REPLACEMENT OF THE CONCEPT OF A SENTENCE AS PUNISHMENT, RETRIBUTION, AND REPRESSION WITH ONE OF REHABILITATION, READAPTATION, AND RESOCIALIZATION. DATA ON OFFENSES AND PUNISHMENTS ARE TABULATED. (DEP)