Most domestic violence (DV) researchers examine professional intervention (e.g., police and nurses), but informal helpers (e.g., friends and bystanders) are critical. The authors measure undergraduates' intervention likelihood, type of involvement (i.e., contact with abuser), and the influence of attribution decisions in DV situations where the abuser's sex is manipulated. Self-esteem and other personal variables are not found to be influential, but participants intervene more when the abuser is male and if they have experienced childhood abuse. The influence of attributions in DV situations is influenced by the sex of the attacker and severity of the attack. Participants' attributions for male attackers predict intervention in severe cases of DV; attributions of drunkenness predict more intervention. In general, informal male helpers choose more risky types of intervention than female helpers do, and more aggressive individuals choose less helpful behaviors than those lower in aggression. Stigma reduction associated with DV and intervention, especially among male victims, and the importance of encouraging appropriate involvement among helpers are discussed.