Applied are empirical findings supporting the authors’ previously presented nomenclature identifying two subsets of sexually abusive youth overlooked by most contemporary risk assessment tools: sexually violent and predatory sexually violent youth. The cross-validation findings on an ecologically framed risk assessment tool, MEGA (Multiplex Empirically Guided Inventory of Ecological Aggregates for Assessing Sexually Abusive Children and Adolescents [Ages 19 and Under]) (N = 1,056 male and female sexually abusive youth, ages 4-19, including youth with low intellectual functioning), from the United States, Canada, England, and Scotland, were utilized. Findings provided normative data, with cutoff scores according to age and gender. Most contemporary risk assessment tools have three levels (low, moderate, and high), which may in fact be limited in assessing the range of risk level. The MEGA cross-validation established a new range of risk level, with the fourth level (very high) definitively identifying the most dangerous youth, thus empirically supporting the nomenclature of sexually violent and predatory sexually violent youth.