The murders and suspicious disappearances of women across Canada over the past forty years have received considerable national attention in the past decade. The disappearances and murders of scores of women in British Columbia, Alberta and Manitoba have highlighted the vulnerability of women to extreme violence. Girls and women of Aboriginal ethnicity have been disproportionally affected in all of these cases and have high rates of violent victimization. The current socio-economic situation faced by Aboriginal women contributes to this. To provide publicly available data of missing and murdered women in Canada, a database was created containing details of 3,329 women, including 824 who are Aboriginal. There are key risk factors that increase the probability of experiencing lethal violence: street prostitution, addiction and insecure housing. The vast majority of sex workers who experience lethal violence are street prostitutes. The dissertation examines the legal status and forms of prostitution in Canada and internationally, as well as the individual and societal impacts of prostitution. A review of current research on violence and prostitution is presented. The thesis provides summaries from 150 serial homicide cases targeting prostitutes in Canada, the U.S., and the U.K. The trends and questions posed by these cases are identified. The cases of the missing women of Vancouver and Robert Pickton are detailed. The key findings from the provincial inquiry into the missing women cases and an analysis of the most egregious failings of the investigations (Projects Amelia and Evenhanded) are discussed. Frequently encountered challenges and common errors, as well as investigative opportunities and best practices of police, and other initiatives and recommendations aimed at non-police agencies are evaluated. The three other RCMP-led projects, KARE, DEVOTE and E-PANA, which are large, dedicated units focused on vulnerable women, are assessed. All Canadian women deserve to live free of violence. For women with vulnerable life histories, violence is a daily threat and a common occurrence. More must be done to prevent violence and to hold offenders responsible when violence has been done. This dissertation is a plea for resources and attention; to turn apathy into pragmatic, concrete action founded on solid evidence-based research.