Findings indicate that the loss of quality girlfriend/boyfriend relationships while on the street, as well as the number of relationships terminated by death, were linked with soft drug use. Histories of physical abuse and criminal victimization by peers, on the other hand, influenced street youths' use of hard drugs. In addition, the effects of various forms of relational strain on hard drug use were conditioned by low self-esteem, delinquent peers, deviant values, and low self-efficacy. In contrast, the link between forms of relational strain and soft drug use were conditioned by greater self-esteem and fewer delinquent peers. It may be that the lack of criminal peers reduces youths' access to harder drugs, making them more likely to rely on soft drugs in coping with their strain. Also, greater self-esteem may be a buffer against them using harder drugs in coping with strain. The findings suggest that parenting interventions are likely to minimize the incidence of relational strain by teaching parents how to create positive family environments. For youths who do turn to the street, counseling programs should aim at minimizing the impact of relational strain. A youth's peer group and personal beliefs must also be addressed in counseling. Interview data were collected between June 2005 and January 2006. Youths were interviewed on the streets, in shelters, and at drop-in centers. Boys composed 65 percent of the sample. Drug-use variables were measured using 1-year frequency items. Four broad forms of relational strain encompassed the number of lost relationships, the quality of lost relationships, victimization by street friends, and background factors. 5 tables, 4 notes, and 39 references