The study objective was to clarify the ethical basis of psychiatric research by outlining conceptual issues and empirical findings related to the ethics of human experimentation. A systematic review of scholarly and empirical literature covering three decades was performed. The ethics of human research has come to be understood in relation to the principles of respect for persons, beneficence, justice, and the ideal of informed consent. Subjects who cannot fully participate in informed-consent processes are especially vulnerable to exploitation. Current dilemmas stem from insufficient attention to the vulnerabilities of mentally ill research participants, problems in applying ethical concepts and guidelines to psychiatric research, and claims of research misconduct. Empirical studies indicate that (1) psychiatric symptoms significantly affect informed consent, (2) psychiatric patients may possess certain strengths with respect to research involvement, (3) proxy decision-making is problematic, (4) informed consent is also difficult to attain with the medically ill and others, (5) patients are motivated to participate in research by the hope of personal benefit, (6) ethical aspects of research are poorly documented, and (7) institutional review processes may not be adequate to protect vulnerable subjects. Psychiatric research can be performed ethically, according to standards set throughout the biomedical and behavioral sciences, so long as researchers and institutions are respectful of special ethical issues in human experimentation and strive to include vulnerable study participants fully in research decisions. However, many gaps in the empirical literature exist regarding the specific nature and implementation of ethics principles in psychiatric research. Efforts to advance both science and ethics, including the study of ethical dimensions of human research itself, are essential for the future of psychiatry.