The study explored the predictive validity of "Multiplex Empirically Guided Inventory of Ecological Aggregates for Assessing Sexually Abusive Children and Adolescents (Ages 4 to 19)" ("MEGA"[eighth note]; Miccio-Fonseca, 2006b), a comprehensive developmentally sensitive risk assessment outcome tool. "MEGA"[eighth note] assesses risk for coarse sexual improprieties and/or sexually abusive behavior in male and female youth ages 4 to 19 years (adjudicated and nonadjudicated), including youth with low (i.e., borderline) intellectual functioning. "MEGA"[eighth note] has 4 distinct risk scales with robust internal consistency reliability on cross-validation: "Risk Scale (0.81)", "Protective Scale (0.78)", "Estrangement Scale (0.79)", and "Persistent Sexual Deviancy Scale (0.74)". Sexual recidivism in cross-validation (N = 1,056) was 8.4%, defined as sexually related probation or parole violation (formal or informal). ROC analysis for Risk Scale demonstrated "MEGA"[eighth note] has good predictive validity (AUC = 0.71, 95% CI of 0.62-0.80, p less than 0.001). Youth with low intellectual functioning scored significantly higher on the "Risk Scale" and "Persistent Sexual Deviancy Scale", highlighting the importance of accurately assessing these youth. (Contains 3 figures and 2 footnotes.)