The concept of confidentiality is fundamental to all forms of psychotherapy. The idea of protecting confidential material goes as far back as the Hippocratic Oath in ancient Greek history. Centuries later, authors continue to assert that "only by maintaining confidentiality can the essential groundwork of trust in treatment be developed" (Hough, 1992, p. 106). Others have even argued that without confidentiality, psychotherapy has no value (Epstein, Steingarten, Weinstein, & Nashel, 1977). Confidentiality in group psychotherapy is more complicated than in individual therapy because self-disclosure is at the core of group therapy and there are numerous people hearing the disclosures. Confidentiality in group therapy, once ignored in the literature on ethics, is gaining more attention as this modality becomes more widely practiced; so too is an acknowledgement that ethical dilemmas surrounding confidentiality in groups are commonplace. This article discusses the major considerations and dilemmas on confidentiality in group psychotherapy. We first review confidentiality broadly and discuss the ethical principles that are related to confidentiality. In the next section, we discuss the complexities of confidentiality in group psychotherapy. Finally, we review research on confidentiality in groups and describe common ethical dilemmas.