In recent years, researchers have focused attention on children who are exposed to domestic violence. Although presently there are no scientifically credible estimates of the national prevalence of children exposed to domestic violence, existing data suggest that large numbers of American children are affected. This article discusses the limitations of current databases and describes a promising model for the collection of reliable and valid prevalence data, the Spousal Assault Replication Program, which uses data collected through collaboration between police and university researchers. Research examining the effects of childhood exposure to domestic violence is also limited by a range of methodological problems. Despite this, however, sufficient evidence from the body of studies exists to conclude that such exposure has adverse effects. The specific effects may differ depending on a host of variables, such as the children's ages, the nature and severity of the violence, the existence of other risk factors in the children's lives (for example, poverty, parental substance abuse), and whether the children are also directly physically abused. In general, childhood exposure to domestic violence can be associated with increased display of aggressive behavior, increased emotional problems such as depression and/or anxiety, lower levels of social competence, and poorer academic functioning. A scientifically credible body of research on the prevalence and effects of childhood exposure to domestic violence is necessary to promote the development of effective interventions and to permit the proper channeling of public and private funds. This article identifies some of the steps that can be taken to build the research capacity necessary to obtain the needed data.