The problems of persons who encounter penal and mental health systems, and sometimes challenge the boundaries of both, are typically extremely complex. Consequently, the assessment process is a critical tool in the successful management of the difficulties presented by this group. Such assessment suggests opportunities for intervention where previous strategies are no longer effective, or have become excessively punitive. This paper provides a brief outline of current assessment aims, a summary of some of the measures used to obtain information about interpersonal behavior in clinical and other settings, and some observations on the study of personality change in such institutions. The paper concludes that, when a moral dimension is implicated in the assessment process, as in the case of offending behavior, intervention requires a multidimensional approach, within which accountabilities for offending are clearly identified. Where the intervention model is conceptually sound, adhered to, targets factors known to be linked with recidivism, and is "responsive" (in matching style and mode of service delivery to the abilities of the offenders), the outcome is quantifiably more successful. Tables, references