Since the 1960’s, the criminal justice system has used psychological, personality-based classification systems to differentially treat and supervise offenders. While responsivity to treatment and prison life are thought to be influenced by personality traits, this remains an under-researched area. The four studies reviewed here measured personality variables via the Jesness Inventory (JI), which collapses personality classifications into four categories for adult offenders: (1) antisocial; (2) neurotic; (3) dependent; and (4) situational. Collectively, the studies probed the viability of using psychological classification systems for adult male prison inmates; whether personality variables were related to recidivism; whether personality impacted success in cognitive programming; and whether the existing JI offender typology could differentiate among child molesters. All studies used samples of adult male offenders. Findings from the individual studies are presented and the authors observe that there is a consistent pattern suggesting that neurotic offenders (high anxiety) are distinct from other offenders in terms of higher self-reported aggression, greater recidivism rates, adverse response to cognitive programming, and lower self-esteem among neurotic child molesters. The findings suggest that personality is an important consideration for inmate programming. The neurotic inmate is an offender type that deserves further research consideration given the results of the four studies examined here. Tables, figures, references