Interdisciplinary research teams gathered data via literature reviews, interviews, site visits, and records reviews starting in 1976. They found the Patuxent Institution to be operating on a dual model containing both custody and treatment components. The concept of defective delinquency entails both a propensity toward criminal behavior and an emotional disorder or intellectual deficiency. However, the research literature indicates that the dual model is inadequate and inaccurate as a basis for treating offenders. It is impossible to predict dangerousness. As a result, indeterminate sentences are being given to many offenders who are not dangerous. In addition, judges vary in their application of the State law on defective delinquency. Patuxent's treatment programs are no more effective than previous programs, and the recidivism rates of Patuxent residents do not differ significantly from those of comparison groups. Patuxent offers modest benefits in comparison to other correctional programs, but it costs substantially more. Patuxent should continue as a special program facility, with modifications both in programming and in referral procedures. Data tables, figures, and 169 references.