In this prospective study, the dutch version of the hcr-20 (an instrument assessing risk factors for violence in the past, present and future) was coded independently by three rater groups (researchers, treatment supervisors and group leaders) for 127 male mentally disordered offenders admitted to a forensic psychiatric hospital. During case conferences, the three raters discussed their ratings and reached consensus on their ratings and final risk judgment. Hcr-20 ratings were related to incidents of physical violence during treatment. Overall, the predictive validity of the hcr-20 was good. We found no differences between researchers and treatment supervisors in predictive accuracy. Group leaders performed worse compared to the other two rater groups. The consensus rating was the best predictor. Implications for structured violence risk assessment in clinical practice are discussed.