Treatment involves the acts and attitudes used to help patients achieve a more realistic solution to their basic problems of accepting themselves and relating to others. The patient's own attitude and participation in the treatment are essential for progress. In Denmark, provision for indeterminate sentencing is intended to isolate and, if possible, to treat a small group of offenders who have shown they are severe threats to society. The value of this approach is that it targets the most difficult cases for specialized treatment by an interdisciplinary team. The first aim of treatment is to kindle optimism and self-respect in the client, to be followed by the second aim: convincing the client that a further attempt at developing socially-acceptable roles has a good chance of success. Treatment further aims at (1) helping clients gain a less-biased understanding of their needs in relation to long-term life goals, accompanied by a new form of inner control in meeting needs; (2) assisting the clients in developing a better use of their personal assets so as to overcome their handicaps and achieve a more acceptable lifestyle; and (3) helping clients form a pattern of fulfilling interpersonal relationships and social roles. A total of 126 property crime detainees from the program (located at Herstedvester and Horsens) were compared with a similar group of property offenders from special and general state prisons. A 5-year followup showed no significant difference in the total recidivism rate; however, 2 years after leaving the institutions, the recidivism rate of the detainees was significantly lower than that of the prisoners. Further, the number of recidivists from among the detainees -- especially the group with the highest risk factors in their previous history -- was statistically lower than for the prisoners who had served normal sentences with fixed terms. The time served was considerably shorter for the prisoners than for the detainees, however (12 months and 32 months respectively). Forty-one footnotes are listed.