CONTRARY TO CONVENTIONAL BELIEFS THAT CORRECTIONAL INSTITUTIONS ARE MERELY 'SCHOOLS OF CRIME' AND THAT INMATES ARE MORE CRIMINALLY ORIENTED ON RELEASE THAN WHEN THEY ENTER THE JUVENILE JUSTICE SYSTEM, THE CONCLUSIONS RESULTING FROM BEFORE-AND-AFTER ANALYSIS OF THE ARREST RATES OF 317 CHICAGO CHRONIC JUVENILE OFFENDERS HANDLED BY THE ILLINOIS DEPARTMENT OF CORRECTIONS (DOC) SHOW THAT IMPRISONMENT DOES DETER FURTHER CRIME BY ABOUT TWO-THIRDS. THIS REDUCTION IN ARREST RATES, CALLED THE 'SUPPRESSION EFFECT,' IS EXAMINED FROM A NUMBER OF PERSPECTIVES FOR ITS VALIDITY IN RELATION TO DETERRENCE DUE TO IMPRISONMENT. FOR EXAMPLE, IS THE DROP IN ARRESTS THE RESULT OF THE JUVENILES' MATURATION (SINCE OFFENDING JUVENILES TEND TO CEASE CRIMINAL BEHAVIOR AS THEY GET OLDER), OF A FREAK CONSEQUENCE STEMMING FROM AN UNUSUAL STUDY POPULATION, OR OF SAMPLE MORTALITY, ETC.? ALTERNATIVE FORMS OF CORRECTIONS OFFERED BY THE COOK COUNTY UNIFIED DELINQUENCY INTERVENTION SERVICES (UDIS) RANGING FROM AT-HOME COUNSELING AND ADVOCACY SERVICES TO RESIDENTIAL PROGRAMS TO OUT-OF-TOWN CAMPS AND INTENSIVE CARE ARE EXAMINED FOR THEIR EFFECTS ON THE RECIDIVISM OF 266 JUVENILES WITH HISTORIES COMPARABLE TO THE DOC SAMPLE. PRIMARY ELEMENTS OF INVESTIGATION WERE FIRST PLACEMENT, OVERALL INTERVENTION HISTORY, AND COMBINATIONS OF SPECIAL INTEREST. ALTHOUGH SELECTION BIASES ARE A PROBLEM IN PRECISE INTERPRETATION, RESULTS POINT TO AN APPARENT TENDENCY OF RESIDENTIAL PROGRAMS TO HOLD DOWN FURTHER ARREST RATES MORE EFFECTIVELY THAN NONRESIDENTIAL PROGRAMS. FINALLY, BEFORE-AND-AFTER ARREST RATES WERE ANALYZED FOR 1,482 JUVENILES PICKED FROM A 1960 BIRTH CHART WHO WERE ORDERED ON SUPERVISION AND PROBATION. PROBATION CLEARLY SHOWED THE WORST POTENTIAL FOR DETERRING FURTHER CRIME, WHILE SUPERVISION RANKED IN A CATEGORY SIMILAR TO UDIS SERVICES. LIMITATIONS OF THE STUDY AND THE FALLACY OF DRAWING QUICK CONCLUSIONS FROM IT ARE DETAILED, BUT THE AUTHORS MAINTAIN THAT EVEN IN THE FACE OF CONVENTIONAL ARGUMENTS ON CORRECTIONAL COSTS, THE STUDY SHOWS THAT A BENEFIT ACCRUES FROM INSTITUTIONALIZATION OF CHRONIC JUVENILE OFFENDERS COMMITTING SERIOUS CRIMES. THE SUPPRESSION EFFECT AND REGRESSION ARTIFACT ARE DISCUSSED IN DETAIL. STUDY DATA AND REFERENCES ARE PROVIDED.