Objective: To present key findings from the Canadian Incidence Study of Reported Child Maltreatment (CIS) in sufficient detail to provide a basis for international comparisons in terms of forms and severity of maltreatment and the age and sex of victims. Method: A survey conducted in a random sample of 51 child welfare service areas across Canada tracked child maltreatment investigations conducted during the months of October to December 1998, produced a national sample of 7,672 child maltreatment investigations. Information was collected directly from investigating workers on child and family background, perpetrator characteristics, severity and types of maltreatment and service and court outcomes of investigations. Results: Forty-five percent of investigations were substantiated and in a further 22% of investigations maltreatment remained suspected. Primary reasons for investigation were physical abuse (31%), sexual abuse (11%), neglect (40%), and emotional maltreatment (19%). A larger proportion of physical abuse cases are isolated incidents involving older children and are more likely to lead to injuries. Sexual abuse, neglect and emotional maltreatment involve more chronic situations with children showing signs of emotional harm. Rates of investigated and substantiated maltreatment are lower in Canada compared to the United States, but are higher than rates reported in Australia. Conclusions: The CIS provides much needed information for developing a better understanding of the profile and needs of children and families investigated by child welfare authorities in Canada. The study also serves as a point from which international comparisons can be made. [Funding for this study was provided by Health Canada, the Governments of Quebec, Ontario, British Columbia, and Newfoundland, and the Bell Canada Child Welfare Research Unit.]