What are the likely mental and related physical health consequences of prolonged exposure to common stressors to detainees at Guantanamo Bay, Cuba? Significant distress leads to high rates of psychiatric disorders, medical problems, and functional impairments. The consequences are severe, physically and psychologically, affecting the individual, his or her family, and the culture at large. Damaging conditions endured by detainees are multiple and severe and are reviewed here in detail. The author identifies parallels between Guantanamo detainees and similarly mistreated populations (e.g., prisoners of war, asylum seekers, prisoners) to draw inferences from existing research regarding likely outcomes for Guantanamo detainees. Protective factors normally present are systematically disrupted at Guantanamo. Overall, it is likely that detainees and their families are experiencing significant mental and physical health problems as a result of overlapping severe and chronic stressors related to detention and that this will worsen over time, particularly in the absence of appropriate assessment and treatment. The author addresses political and ethical factors, as well as basic implications for assessment, treatment, and advocacy, although these are not the focus of the article. Researchers and clinicians will face challenges in providing care for this population and understanding the long-term effects of such mistreatment. Sources reviewed are current up to September 2009.