Young injection drug users (IDU) are at high risk for viral infections, such as HIV, hepatitis C virus (HCV), and hepatitis B virus (HBV), due to frequent injecting, needle/syringe and other drug preparation equipment sharing, high numbers of sexual partners, and exchange of sex for money or drugs. Street youth who inject have high unemployment, poor education, and mental health issues. In San Francisco, young IDU are typically homeless runaways who often are involved in an illegal street economy, including prostitution, drug sales, theft, panhandling, pornography and selling stolen property. They experience a large number of negative and traumatic events prior to leaving home. Many fear and mistrust authority and consequently avoid or delay contact with the public health system. The combination of youth, drugs, survival sex and disenfranchisement make this group extremely vulnerable to multiple negative health outcomes.