Addressing sexual assault requires policy and practice responses that are well-informed and empirically-grounded. This study examines the impact of perpetrators' drug and alcohol use during and after sexual assault. A representative sample of women, who responded to a random digit dialing survey, and reported that they were sexually assaulted at some time in their lives were utilized. The survey questions were drawn largely from The National Violence Against Women (NVAW) Survey (Tjaden 1996), and a series of binary logistic regressions was conducted to determine the impact of perpetrators' alcohol and drug use on violence before and after the assault. Findings indicate that perpetrators' alcohol or other drug use at the time of the assault resulted in a greater likelihood of concurrent violence, including hitting, slapping, kicking, use of a weapon, threats to harm or kill, and physical injury during the assault, and as a result, assault victims experienced more time lost from work, school, home duties, and recreation. Both these impacts occurred regardless of the relationship of the perpetrator to the victim, location of the sexual assault, or the victim's ethnicity. This information assists advocates and policy makers in prevention efforts where sexual violence is more likely to emerge.