Mass casualties’ events result in protracted psychopathology in a significant proportion of exposed individuals, which community-based resilience-promoting interventions may mitigate but not eliminate. Survivors with prolonged mental health sequelae remain, therefore, a major long-term burden on individuals, families and the society at large. Early cognitive behavioral interventions may reduce the proportion of affected survivors but are prohibitively costly and marginally efficient when provided unselectively. Consequently, an efficient prevention critically hinges on the capacity to reliably identify survivors at significant risk. Several risk indicators have been identified (e.g., female gender, prior trauma exposure, exposure type or severity, early symptoms’ configuration and severity). These group-level estimators, however, do not inform survivors’ personal outcome. Indeed, their underlying classification models explore parameters that differentiate cases (future PTSD) from non-cases (no future PTSD) – an impossible task given predictors diversity, interdependence, and the limited variance explained by each. Seeking an alternative to case prediction, the International Consortium to Predict PTSD (ICPP) pooled data from 16 acute-care-based longitudinal studies towards developing a risk estimate model, capable of quantifying prolonged PTSD likelihood for each survivors (i.e., “How likely is that survivor to develop PTSD”). Using survivors’ early PTSD symptoms, gender, lifetime trauma history and educational attainment to predict nine to fifteen months’ PTSD, the ICPP group developed a simple, web-based risk assessment tool that applies to every trauma survivor. Because it addresses a single traumatic events in civilians admitted to acute care services, the ICPP tool requires re-calibration and adjustments to inform mass casualty trauma. It nonetheless exemplifies the advantage of replacing case prediction by risk likelihood estimates, and provides a reliable assessment tool for acute care trauma survivors.