The study proposes a risk-amplification model (Whitbeck et al., 1999) to examine the negative effects of early sexual abuse on illicit drug use on the street among female homeless and runaway adolescents. This model suggests that homeless adolescents have their "basic training" in coercive/abusive families and will carry this interaction pattern into the street, thereby setting in motion a negative chain of events. Sexual abuse that the subjects had experienced while living at home was measured with Whitbeck and Simons' early sexual abuse scale. Most early sexual abuse was found to have occurred between 8 and 12 years old. The average age for running away from home was 13.55. Consistent with previous research, this study found high rates of drug use, especially marijuana use, among the sample. The negative effects of early sexual abuse on later drug use were supported. Although the prevalence of drug use was similar between female adolescents with and without sexual abuse histories, those with sexual abuse histories were more likely to be multiple drug users. Cocaine was more likely to be used by the sexually abused women. Early sexual abuse directly increased the probability of running away at an earlier age and spending more time on the streets. A direct effect was also found between early sexual abuse and risky sexual activities. Adverse environments and a lack of resources forced the youth to connect with others similar to themselves, and they cooperated in reinforcing deviant subsistence strategies, including drug use. The authors project that continued involvement in high-risk behaviors may lead some of the youth to become chronic drug users and part of the adult homeless population. 4 tables, 2 figures, and 61 references