Two of the surveillance systems - the U.S. National Incidence Study of Child Abuse and Neglect (NIS) and the Canadian Incidence Study of Reported Child Abuse and Neglect (CIS) survey child protection workers regarding their investigations of alleged child maltreatment. These two systems use serial cross-sectional survey of professionals in order to estimate the number of children maltreated in a given year. The third surveillance system, the U.S. National Child Abuse and Neglect Data System (NCANDS), uses administrative data methods in collecting annual case-level and State data. It relies on State information systems pertinent to reported cases of child maltreatment. Each of the three data collection systems makes unique and important contributions in documenting the prevalence of child maltreatment. The CIS collects the most detailed information about the investigated child, including information on three forms of child maltreatment and 22 possible child-functioning concerns. All three of the systems collect detailed information on the demographics of the caregivers and possible risk factors. The CIS and NIS collect information on injuries, although neither system estimates child fatalities; and the NCANDS reports only on maltreatment fatalities. NCANDS allows for children to be identified across multiple investigation events both within an across submission years. The large sample size included in the NCANDS dataset and its continuous census collection allows researchers to explore substantive issues, such as what leads to a recurrence of child abuse/neglect and factors that influence access to services, along with providing data on trends. 1 table, 1 figure, and 33 references