The following is a cost analysis of one month of emergency room treatment provided for different types of injuries at two public hospitals in Rio de Janeiro. The study focused on the following: 1) costs at each hospital for treatment of different injuries (annual and monthly estimates); 2) mean cost of each injury; 3) detailed itemized costs of care (materials and drugs, surgery, standard procedures, tests, professional fees, and meals). The items were investigated at the respective hospitals and included services, materials, and resources employed in treating the 1,053 patients included in the sample (498 in the Miguel Couto Municipal Hospital ­ MCMH ­ and 555 in the Salgado Filho Municipal Hospital ­ SFMH). Traffic accidents (run-over pedestrians, motor vehicle collisions, and transportation accidents) accounted for 74.3% of costs at MCMH and 48.4% at SFMH. Injuries due to aggression were also considered relevant in the cost profile, mainly at SFMH (49% of costs due to violence) as compared to 24.9% of the total care costs at MCMH. Mean treatment costs for pedestrians run over by motor vehicles varied from R$77.76 (SFMH) to R$237.77 (MCMH). Mean treatment costs for victims of aggression varied from R$107.35 (SFMH) to R$84.19 (MCMH). The study suggests public health measures to deal with and prevent violence.