The ethics of involving persons with cognitive impairments and/or mental illness in research continues to gain academic and public attention. Concerns about the ability of such persons to provide ethically and legally valid consent and about the appropriateness of their research involvement in certain categories of studies have resulted in publication of guidelines, position papers, standards, and court decisions. These analyses address not only when and from whom informed consent may be obtained but also under what conditions it is ethically (...) permissible to involve persons in research who are too decisionally impaired to provide their own consent.It is an advance in research ethics that there is heightened appreciation of the need for greater protections for, and possibly research participation limitations on, persons unable to give their own consent. In our zeal to protect potentially vulnerable subjects, however, we must craft new protections carefully. Prudence is required in shaping and implementing any new protections. (shrink)