This study aimed to identify factors that influenced retention in the National Institute on Drug Abuse–funded Women and Trauma Study, conducted within the Clinical Trials Network (CTN). Women (N = 346) were recruited from and received treatment in 6 CTN-affiliated sites. Log-linear and logistic models were used to explore factors associated with retention. The mean number of treatment sessions attended was 6.8 (SD = 3.9). Women with more education, higher attendance at 12-step meetings, and strong therapeutic alliance between facilitator and participant had better retention rates. Significant site differences were found; the site with the highest retention rate provided child care and had the lowest average monthly intake. To retain women with histories of trauma and substance abuse in “real world” psychiatric settings, emphasis on regulating individual-level and site-related modifiable variables are crucial.