Transgender women have a higher prevalence of drug use, HIV, drug use, and sex work than the general population. This article explores the interaction of these variables and discusses how sex work and drug use behaviors contribute to the high rates of HIV. A model predicting HIV rates with sex work and drug use as well as these behaviors in the transgender woman's social network is presented. Challenges to intervening with transgender women, as well as suggestions and criteria for successful interventions, are discussed.