We tested hypotheses that social living arrangement and drug use in one's network are independently associated with entry into opiate agonist treatment modalities. Injection drug users (IDUs) attending the Baltimore Needle Exchange Program who received a referral for drug abuse treatment were studied. Baseline interviews, HIV testing, and the Addiction Severity Index (ASI) were administered. Agency records were used to confirm entry into a treatment program offering opiate agonist maintenance therapy within 30 days of the baseline interview. Logistic regression was used to identify predictors of treatment entry. To date, of 245 IDUs, 39% entered such a program. Multivariate logistic regression models controlling for age and intervention status revealed that compared to individuals who lived alone, in a controlled, or nonstable environment (e.g., streets, abandoned house, transitional housing program, or boarding house), individuals who lived with a sexual partner were 3 times more likely to enter treatment (adjusted Odds Ratio [aOR]=3.04; p=0.013) and those who lived with family or friends were almost 3 times more likely to enter treatment (aOR=2.72; p=0.016). In the bivariate analyses, a marginal association was observed between being responsible for children or others and entry into treatment (p=0.066); however, this association was not significant in the multivariate model. Findings from this study suggest that supportive living environments may facilitate entry into treatment and may be helpful in devising appropriate and targeted interventions to encourage drug treatment entry.