Objective: To determine trends for in-hospital survival and functional outcomes at acute care hospital discharge for patients with severe adult traumatic brain injury (SATBI) in Pennsylvania, during 1998 to 2007. Methods: Secondary analysis of the Pennsylvania trauma outcome study database. Main Outcome Measures: Survival and functional status scores of 5 domains (feeding, locomotion, expression, transfer mobility, and social interaction) fitted into logistic regression models adjusted for age, sex, race, comorbidities, injury mechanism, extracranial injuries, severity scores, hospital stay, trauma center, and hospital level. Sensitivity analyses for functional outcomes were performed. Results: There were 26 234 SATBI patients. Annual numbers of SATBI increased from 1757 to 3808 during 1998 to 2007. Falls accounted for 47.7% of all SATBI. Survival increased significantly from 72.5% to 82.7% (odds ratio [OR] = 1.10, 95% CI: 1.08–1.11, P < .001). In sensitivity analyses, trends of complete independence in functional outcomes increased significantly for expression (OR = 1.01, 95% CI: 1.00–1.02, P = .011) and social interaction (OR = 1.01, 95% CI: 1.00–1.03, P = .002). There were no significant variations over time for feeding, locomotion, and transfer mobility. Conclusions: Trends for SATBI served by Pennsylvania's established trauma system showed increases in rates but substantial reductions in mortality and significant improvements in functional outcomes at discharge for expression and social interaction.