Mental patients have often been treated worse than criminals during many periods of history. Until the 1970's, mental patients were often denied many of the constitutional rights accorded to criminal defendants. In the current era of deinstitutionalization and community care, mental patients have too often fared poorly. Mental patients and ex-patients are also victimized by stigmatizing attitudes and discriminatory behaviors. Mental patients also have arrest rates higher than the general population, according to a variety of studies. However, patients without prior arrests have been found to have arrest rates lower than for the general population. In addition, expatients pose less of a crime threat than do ex-convicts. A variety of theories have been advanced to explain the proportions of the prison population that is mentally ill. A further aspect of the study of mentally ill persons as victimizers is the burden they may place on the community as a result of community saturation, ex-patients as a public nuisance, and possible property value declines in saturated communities. The recent blurring of distinctions between criminal behavior and psychopathological behavior is resulting in the emergence of the concept of a new marginal population in which the distinction between victims and victimizers is difficult to make. Seventy-eight references are listed.