This NIJ Special Report describes the most common types of batterer intervention programs and evaluates two recent studies of batterer intervention programs in Broward County, Florida and Brooklyn, New York. Evaluations of both programs call into question the effectiveness of such programs in either changing batterer attitudes or behaviors. However, researchers in the Broward study did find that batterers who were employed, married, owned their own homes, or otherwise had a stake in the community were less likely to reoffend. Although the Broward study was marred by low victim response rates, collection of information from multiple sources, each reaching similar conclusions, bolstered researchers' confidence in the results. The Brooklyn study showed that men who attended treatment sessions for a longer period (26 weeks compared with 8 weeks) committed fewer new violent acts; however, batterers were more likely to complete the shorter program. The study left open the question of whether batterer intervention programs alter batterers' attitudes and behaviors or merely suppress violence behavior for the duration of the study.