Classification of the mentally deficient delinquent may be perhaps most easily arrived at by the psychological standards of the Binet system. This system has been in use in some of the feeble-minded institutions of the country, and has been used by the New Jersey Reformatory the past year; there may be some other reformatories that have also used it with most satisfactory results. Each inmate in the Reformatory of New Jersey, received during the year, has been subjected to the Binet tests, and this determining of a psychological age has established the fact that 46% of the inmates received during the last year are mentally subnormal. The physical age at which delinquents may be legally committed to the reformatory is sixteen to twenty-five years. But by examination it has been discovered that the mental age for nearly a majority was below twelve years, while in one case it was less than five. In other words, 46% of those received had minds which in knowledge and ability were only equal to the minds of the child from five to twelve years old. By the system employed, they have been classified in the precise year between these two limitations, to which they mentally belong. There is, however, without question one point at which the system needs to be taken with a considerable degree of care. Of the 46% who were mentally deficient, according to the tests, it was found by a study of the history of these cases that 17½% had received only a year’s schooling or less. What their minds would have been if they had not had this misfortune could not be determined by the system, but could only be arrived at when they had been given the opportunity of an education. From this data, it would seem wise to divide the 46% mentally defectives into two classes. First: The hopelessly defective or feeble-minded delinquent, of whom there were 28½%. Second: The hopeful cases of defectives, possibly capable of development into normals with proper training, of whom there were 17½%.