THERE ARE MORE THAN 230,000 ADULT MALES AND FEMALES INCARCERATED IN STATE PRISONS. THE MAJORITY ARE UNDEREDUCATED, UNDERSKILLED, AND FROM CULTURALLY AND FINANCIALLY IMPOVERISHED BACKGROUNDS. THE INCIDENCE OF MENTALLY RETARDED MALE INMATES ENTERING THE CORRECTIONAL SYSTEM IS ESTIMATED TO BE 10 PERCENT. RETARDED INMATES TEND TO BE OLDER, AND 8 OUT OF 10 ARE EITHER BLACK OR MEXICAN-AMERICAN. FOR MENTALLY RETARDED INDIVIDUALS ACCUSED OF A CRIME, LAWS OF INCOMPETENCY POSE SPECIAL PROBLEMS. SUCH LAWS ARE DESIGNED MORE FOR THE MENTALLY ILL OR THE INSANE THAN FOR THE MENTALLY RETARDED. THEY DO NOT RECOGNIZE MENTAL RETARDATION PER SE AS A MENTAL CONDITION THAT RENDERS AN ACCUSED INCOMPETENT TO STAND TRIAL. THE INSANITY DEFENSE FOR MENTALLY RETARDED PERSONS PRESENTS MANY OF THE SAME BASIC PROBLEMS AS LAWS OF INCOMPETENCY: (1) THERE IS THE QUESTION OF WHETHER MENTAL RETARDATION IS OR SHOULD BE A MENTAL CONDITION THAT EXCUSES A PERSON FROM CULPABILITY; (2) IF A MENTALLY RETARDED PERSON IS EXCUSED FROM CULPABILITY, THERE IS THE QUESTION OF WHAT CIRCUMSTANCES MAKE IT PERMISSIBLE FOR THE STATE TO COMMIT THAT PERSON TO A MENTAL INSTITUTION; AND (3) THERE IS THE ISSUE OF HOW LONG THE STATE CAN CONFINE A MENTALLY RETARDED DEFENDANT ACQUITTED BY THE DEFENSE FOR REASON OF INSANITY. THE WAY IN WHICH STATUTES ARE WRITTEN INFLUENCE THE HANDLING OF MENTALLY RETARDED OFFENDERS. LESS THAN 10 PERCENT OF ALL CASES INVOLVING THESE OFFENDERS, BOTH FELONY AND MISDEMEANOR, RESULT IN A JURY TRIAL. SINCE PRISONS ARE NOT DESIGNED TO TREAT THE MENTALLY RETARDED, LITTLE PROGRAMMING EXISTS THAT MEETS THIS GROUP'S SPECIAL NEEDS. FURTHERMORE, THE LOW FUNDING PRIORITY OF MOST CORRECTIONAL SYSTEMS INSURES THAT PROGRAMS MUST BE GEARED TO THE AVERAGE RATHER THAN THE RETARDED INMATE. RESEARCH TO EVALUATE ALTERNATIVES IN THE HANDLING OF MENTALLY RETARDED PERSONS SHOULD BE CONDUCTED WITH REGARD TO THE TOTAL NEEDS OF A STATE OR AREA, OPERATING CAPACITY OF THE INSTITUTION, AND PERCENTAGE UTILIZATION OF THE OPERATING CAPACITY. REFERENCES ARE INCLUDED.