The new definitions and procedures in substantiation determinations performed well in the field trial. Agreement between master reviewers’ expert case determinations and field sites’ determinations was very high across all forms of child maltreatment. Determinations from five field sites were compared with those of master reviewers. Agreement, sensitivity, specificity, positive predictive values, and negative predictive values were high overall and for each form of maltreatment. Agreement was substantially improved. Substantiation determinations lie at the center of child welfare services and policies. The decision to substantiate a case of maltreatment is pivotal. A substantiated case of maltreatment is considered “real” by policymakers, administrative systems, researchers, and families themselves. However, research has consistently suggested that determinations are at best, unreliable. Tables, appendix and references