The effects of an intramural cognitive-behavioral treatment for forensic inpatients with personality disorders in a high-security hospital were examined. Treatment was aimed at modifying maladaptive coping and social skills, at enhancing social awareness, at reducing egoistic and oppositional behaviors, and at reducing psychological complaints. The patients, who all had committed serious crimes (violence, arson, sexual offences), participated voluntarily in the study. A total of 39 patients started the study, but during the course of the study, several patients dropped out because of several reasons. Patients as a group showed significant improvements over time on psychopathological symptoms, personality traits, and coping. A significant decrease of oppositional behaviors was reported by the staff. Though the patients improved well at the group level, only a minority of patients showed reliable change over time at the individual level. The meaning of the results in relation to treatment are discussed.