The Optimus Study is a cross-national initiative on child sexual victimization in the context of other forms of maltreatment, and aims to provide much-needed evidence on the risks and protective factors for children and youth. Its goal is ultimately to reduce the incidence of abuse and improve services for those affected by applying the best social science research methods available to create an evidence base in order to influence policy, practice, and funding. The Optimus Study has successfully developed a research model that integrates standardized population-based survey methods with health and social statistics tracking to assess prevalence and response rates (Agency Survey), as well as a framework to advance the field through translating the knowledge generated by the research into policy and practice. It also strives to advance international epidemiology research on violence against children. The population survey in Switzerland collected lifetime and previous-year prevalence of sexual victimization experiences for a nationally representative sample of youth from 15-17, as well as information on other types of maltreatment, risk factors, protective factors, and consequences of victimization.