Traumatic brain injury (TBI) is a major cause of morbidity and mortality in the United States. Each year, on average, TBIs are associated with an estimated 1.1 million emergency department visits, 235,000 hospitalizations, and 50,000 deaths in the United States. For 2002, the overall rate of TBI-related hospitalization reported by the 12 states in the CDC TBI surveillance system was 79.0 per 100,000 population; across these states, however, the rates varied substantially (from 50.6 in Nebraska to 96.9 in Arizona). To update results from the CDC TBI surveillance system, CDC analyzed data from 2003, the most recent year for which data were available. This report summarizes the results of that analysis, which indicated that an estimated 28,819 persons (87.9 per 100,000 population) were hospitalized with a TBI-related diagnosis in the nine states that reported data for 2003. For all age groups combined, rates were higher among males. Age-specific rates were highest among persons aged >/=75 years. Unintentional motor-vehicle-traffic incidents (MV-T) and unintentional falls were the two leading causes associated with TBI-related hospitalization. The findings underscore the need for states to continue monitoring the occurrence, external causes, and risk factors for TBI and to design and implement more effective injury-prevention programs.