THE PATUXENT INSTITUTION OPENED IN 1955 TO PROVIDE AN INTENSIVE REGIME OF MEDICAL, PSYCHIATRIC, AND THERAPEUTIC SERVICES FOR ADULT MALE OFFENDERS TERMED 'DEFECTIVE DELINQUENTS.' INMATE CAPACITY IS 500 AND THE STAFF INCLUDES MORE PSYCHIATRISTS, PSYCHOLOGISTS, AND SOCIAL WORKERS THAN ARE FOUND (ON A PER-INMATE BASIS) IN ANY OTHER UNITED STATES PRISON. PROGRESS AND PARTICIPATION IN THERAPY PROGRAMS IS REWARDED BY ADVANCEMENT TO THE NEXT 'GRADED TIER'; EACH TIER CONSISTS OF INCREASING INCREMENTAL PRIVILEGES SUCH AS UNLOCKED DOORS AND COLOR TELEVISION. SIMILARLY, RELEASE FROM PATUXENT IS GRADUAL, FIRST TO A PRERELEASE CENTER ON THE GROUNDS. THE STUDY WAS DESIGNED TO DETERMINE PATUXENT'S IMPACT ON POSTRELEASE CRIMINAL BEHAVIOR. THE TREATMENT SAMPLE INCLUDED INMATES PAROLED IN 1971 TO 1972, TOTALING 106 INMATES. THE COMPARISON SAMPLE CONSISTED OF 54 OFFENDERS DIAGNOSED AT PATUXENT AS 'DEFECTIVE DELINQUENTS' BUT NOT SO ADJUDGED BY THE COURTS AND THEREFORE SENT TO PRISON. A STATISTICAL MODEL CAPABLE OF DISTINGUISHING BETWEEN CRIME PREVENTION AND CRIME POSTPONEMENT WAS EMPLOYED. ANALYSIS SHOWED THAT PATUXENT OFFERS BOTH PREVENTION AND POSTPONEMENT BENEFITS WHEN COMPARED TO PRISON. COST CALCULATION FOCUSED ON CONSTRUCTION, MAINTENANCE, AND OPERATION COSTS OF THE CORRECTIONAL INSTITUTION AND THE FOREGONE ANNUAL EARNINGS OF THE OFFENDERS CONFINED THERE (ESTIMATED AT $8,900 PER INMATE). PATUXENT SHOWS A 6 PERCENT REDUCTION IN THE ULTIMATE PROBABILITY OF REARREST AND A 1 YEAR POSTPONEMENT OF REARRESTS. THESE BENEFITS ARE PURCHASED AT A COST TO THE STATE OF AT LEAST $38,000 PER INMATE. SOME OF PATUXENT'S ACTIVITIES SUCH AS ELABORATE SUPERVISION OF RELEASES ARE, THEREFORE, COST-EFFECTIVE AND SHOULD PROVIDE MODELS FOR CONVENTIONAL CORRECTIONAL PROGRAMS. REDUCTION OF CONFINEMENT LENGTH WOULD PROBABLY PRODUCE EQUIVALENT BENEFITS BUT AT A REDUCED COST. NOTES AND REFERENCES ARE INCLUDED IN THE EVALUATION. (LWM)