Longer treatment duration has consistently been related to improved substance use outcomes. This study examined how tailored women's programming and organizational characteristics were related to duration in outpatient substance abuse treatment in women. Data were from two waves of a national outpatient substance abuse treatment unit survey (n = 571 in 1999/2000, n = 566 in 2005). Analyses were conducted separately for methadone and nonmethadone programs. Negative binomial regressions tested associations between organizational determinants, tailored programming, and women's treatment duration. Of the tailored programming services, childcare was significantly related to longer duration in the nonmethadone programs, but few other organizational factors were. Tailored programming was not associated to treatment duration in methadone programs, but ownership, affiliation, and accreditation were related to longer duration. Study findings suggest evidence for how external relationships related to resources, treatment constraints, and legitimacy may influence women's treatment duration. Methadone programs may be more vulnerable to external influences. © 2009 Elsevier Inc. All rights reserved.