THE SUBJECTS' AGES RANGED FROM 13 TO 18, THE DURATION OF THEIR STAYS IN THE INSTITUTION FROM 3 MONTHS TO 4 YEARS. THEIR OFFENSES INCLUDED THEFT, ILLICIT DISTILLATION, RUNNING AWAY, AND PROSTITUTION. ON THE BASIS OF IQ (INTELLIGENCE QUOTIENT) SCORES, THE YOUTHS WERE CATEGORIZED AS NONRETARDED (IQ OF 63 OR HIGHER) OR MILDLY RETARDED (IQ OF 46 TO 62). THE MEAN IQ FOR THE RETARDED GROUP WAS 57, FOR THE NONRETARDED GROUP 70. NO SIGNIFICANT DIFFERENCES BETWEEN THE TWO GROUPS IN TYPES OF CRIMES COMMITTED, PATTERNS OF FAMILY DISORGANIZATION, OR ADVERSE ENVIRONMENTAL FACTORS (LOW SOCIAL CLASS, CRIMINAL RELATIVES, ALCOHOLIC PARENTS) WERE FOUND. IT IS CONCLUDED THAT, WHILE MILD MENTAL RETARDATION DOES NOT APPEAR TO BE A SIGNIFICANT FACTOR IN THE ETIOLOGY OF DELINQUENCY, IT SHOULD BE TAKEN INTO CONSIDERATION IN ASSESSING DELINQUENTS AND PLANNING FOR THEIR TRAINING. EMPHASIS SHOULD BE PLACED ON HELPING MILDLY RETARDED YOUTHS ACQUIRE JOB SKILLS. SUPPORTING DATA AND A LIST OF REFERENCES ARE PROVIDED. (LKM)