This study tests the impact of coordinated community response (CCR) on reducing intimate partner violence (IPV) and on modifying knowledge and attitudes. The authors conduct hierarchical linear modeling of data from a stratified random-digit dial telephone survey (n = 12,039) in 10 test and 10 control sites, which include 23 counties from different regions in the United States, to establish the impact of a CCR on community members' attitudes toward IPV, knowledge and use of available IPV services, and prevalence of IPV. Findings indicate that CCRs do not affect knowledge, beliefs, or attitudes of IPV, knowledge and use of available IPV services, nor risk of exposure to IPV after controlling for age, gender, ethnicity, income, and education. Women in communities with 6-year CCRs (as opposed to 3-year CCRs) are less likely to report any aggression against them in the past year. These results are discussed within the context of evaluation challenges of CCRs (e.g., IPV activities in comparison communities, variability across interventions, time lag for expected impact, and appropriateness of outcome indicators) and in light of the evidence of the impact of other community-based collaborations. (Contains 4 tables and 1 figure.)