Violence risk assessment has advanced considerably in the last 20 years. In the 1980s, leading professionals questioned the very possibility of valid violence risk assessments; now, many of the major risk factors have been identified, and professional debate focuses on how best to combine these risk factors into meaningful evaluations. An important contributor to this advance in knowledge has been the rise of meta-analytic reviews. Through quantitative summaries, the cumulative findings of small, potentially insignificant studies have provided important answers to questions concerning the effective assessment and treatment of violent offenders.