The findings suggest that young people should be the prime focus of interventions to reduce the number of new injectors; urgent interventions are needed for youth who show personal vulnerability and live in extremely precarious conditions that offer little or no alternatives to the streets. The analysis of the predictors of initiation into drug injection showed that the most important independent predictor was having consumed at least four different types of drugs. This factor may be an indication of a young person whose individual profile makes him or her particularly inclined to try various drugs in search of the ultimate high/effect. Trying injection appeared to be part of the consumption experiences of certain young people eager for the strong sensations that one gets from psychotropic drugs. Another factor linked to substance use that was found to represent an independent predictor of drug injection was recent daily alcohol consumption. This result is consistent with the hypothesis of an increased risk of injection among youth who are involved in intensive substance consumption. It may also be possible that a young person under the influence of alcohol is more inclined to experiment with drug injection than when sober. Having recently been homeless was another predictor of initiation into drug injection. Finally, survival sex was an independent predictor of initiation into injection among adolescent street youth. Individual and structural elements are involved in the initiation into drug injection in adolescent street youth. Life conditions on the street and the few legal opportunities adolescents have to meet their needs clearly enhance their vulnerability to risky behaviors. Living on the streets, especially in large urban centers where drugs abound can lead adolescents to start injecting. Data were collected from interviews with youths seeking free services from community organizations. Limits are discussed. Tables, references