Transgender people have been disproportionally affected by HIV, particularly transgender women. Their increased vulnerability to HIV is due to multiple issues, including biological (eg, increased efficiency of HIV transmission through receptive anal sex), epidemiological (eg, increased likelihood of having HIV-infected partners), structural (eg, social stigma limiting employment options), and individual factors (eg, internalized stigma leading to depression and substance use and risk-taking behaviors). There have been limited culturally appropriate HIV prevention interventions for transgender people, with many key prevention studies (eg, the iPrEx PrEP study) enrolling transgender women in a study focusing on men who have sex with men. This has resulted in limited understanding of the optimal ways to decrease transgender people's risk for HIV acquisition. The current supplement of JAIDS is designed to review what is known about HIV prevention for transgender people and to highlight new insights and best practices. The study reviews recent epidemiologic data, the pharmacology of HIV prophylactic agents in individuals who may be using exogenous hormones, and several recent multi-component interventions designed to address the lived experience of transgender people. Additionally, the study reviews the work going on at the NIH to address transgender health in general and HIV prevention in specific, as well as two important papers related to clinical trial design issues and the ethical conduct of research in this frequently disenfranchised population. It is the hope of the HIV Prevention Trials Network (HPTN) that this supplement will promote new knowledge around transgender health and the requisite issues that need to be addressed in order to conduct optimal clinical trials. The ultimate hope is that the information distilled in this supplement will inform investigators, clinicians, and public health officials in order to design further research to develop optimal prevention interventions for transgender people and to implement these interventions in ways that are culturally congruent and health promoting.