Objective: The authors examine the effects of batterer intervention program (BIP) completion on domestic violence re-arrest in an urban system of 30 BIPs with a common set of state standards, common program completion criteria, and centralized criminal justice supervision. Method: 899 men arrested for domestic violence were assessed and completed 1 of 30 BIPs. At 2.4 years after intake, the authors reviewed arrest records and modeled domestic violence re-arrest using instrumental variable estimation and logistic regression. Results: There were 14.3% of completers and 34.7% of noncompleters re-arrested for domestic violence. Completing a BIP reduces the odds of re-arrest 39% to 61%. Conclusions: This study supports efforts to engage and retain men in gender-specific BIPs, as well as the value of examining larger systems of BIPs. (Contains 1 figure and 3 tables.)