Aggression against nurses and ancillary personnel is a major--overall under-reported--occupational problem in sociomedical facilities for psychiatric and demented patients. The frequency of violent incidents against workers in a residential rehabilitation unit was assessed during medical examinations in the workplace between 1996 and 2009. The majority of the workers had been subjected to physical aggression over time. A violence prevention program that included educational, organizational, and medical measures was implemented in 2002. Interrupted time series analysis showed that the aggression trend prior to intervention was flat (beta3 = -0.004; SD = 0.003; P = 0.241), while there was a significant drop in aggressions after the intervention (beta3, = -0.149; SD = 0.018; P < 0.0001). No late increase in trend was observed in the post-intervention period (beta3, = -0.006; SD = 0.004; P = 0.175). The program contributed to reducing violence in the workplace.