With over two decades of child sexual abuse (CSA) research, the actual extent of CSA still remains unknown. However, recent research has indicated that children and adolescents are a good source of information for exposure to CSA. This paper examines the strengths and limitations of data sources used to determine the prevalence or incidence of CSA, as well a outlining some of the ethical and methodological difficulties in asking children directly about abuse or maltreatment. The primary objective of this paper is to review the psychometric properties of instruments designed to ask children about CSA. The paper reviewed data extracted from official sources/records, retrospective reports of CSA obtained from clinical or legal samples (i.e., psychiatric patients, correctional inmates), and the direct inquiry of children about their experiences of victimization. In reviewing the methods used above, the paper than examines the impact to children when asking them questions about their experiences, the researcher’s responsibilities, the accuracy of child reports, and methods of data collection (i.e., psychometric properties of measures, face-to-face interview technique, self-administered questionnaire, telephone interviews). In summation, even though questions or instruments have been developed and used to assess maltreatment in youth, most have not been subjected to rigorous evaluation. A fundamental first step in ensuring accurate estimates on the extent of CSA requires establishing the validity and reliability of instruments used to measure CSA, as well as other forms of victimization. References and appendixes