Imprisonment of offenders with mental disorders in special psychiatric units constitutes a practice expected to satisfy both the legal and medical needs of prisoners. However, the actual conditions in which this practice takes place frequently hinders its purpose. In this work we describe the observations made by members of a Human Right Organization' Mental Health Team, the Centro de Estudios Legales y Sociales (CELS) (Legal and Social Studies Centre), in the Psychiatric Unit of the J. T. Borda Hospital, in Buenos Aires, Argentina. Observations were carried on in three visits performed by a group of psychologists, psychiatrists and lawyers. Visitors interviewed patients and examined the buildings and other material conditions to which patients are submitted. Interviews always took place in front of the guardians. From the interviews and the examination of the installations it can be concluded that: a) patients lack systematic diagnostic and treatment, and b) severe violations to their human rights were documented. So, the imprisonment conditions preclude any therapeutic intervention. The international legislation related to this special clinical and legal situation is revised ant the concepts of "penal state", "control societies" and "total institutions" are discussed.