STUDY OBJECTIVE: We characterize the neurocognitive function of patients presenting to the emergency department (ED) with mild traumatic brain injury. METHODS: This prospective study took place at an urban, academic ED and Level I trauma center. Case patients consisted of a convenience sample of ED patients aged 18 to 59 years, presenting to the ED with mild traumatic brain injury and having a head computed tomography scan without traumatic abnormalities. Controls consisted of patients aged 18 to 59 years, presenting to the ED with an isolated, nondominant hand extremity injury. We excluded patients with multiple injuries and recent alcohol consumption. Subjects completed a computerized neurocognitive test battery (Immediate Post-concussion Assessment and Cognitive Testing). The primary measures were verbal memory, visual memory, and visual motor and reaction speed. We compared raw and age-normalized neurocognitive performance between case patients and controls by using nonparametric statistics. RESULTS: We included a total of 23 head-injured case patients and 31 non-head-injured controls. Case patients and controls exhibited similar raw (median 80.1 versus 85.0 points; difference in medians -4.9; P=.26) and age-normalized (31.9 versus 57.4 percentile; difference in medians -25.5; P=.12) verbal memory. Case patients and controls exhibited similar raw (64.6 versus 63.5; difference 1.1; P=.79) and age-normalized (20.8 versus 25.8 percentile; difference -5.0; P=.44) visual memory. Compared with controls, mild traumatic brain injury case patients demonstrated slower raw (31.6 versus 37.0 points; difference -5.4; P=.002) and age-normalized (17.1 versus 57.6 percentile; difference -40.5; P=.001) visual motor speed. Mild traumatic brain injury case patients exhibited slower raw (median 0.66 versus 0.60 seconds; difference 0.06; P=.01) and age-normalized (29.3 versus 42.8 percentile; difference -13.5; P=.009) reaction times. CONCLUSION: In conclusion, compared with the non-head-injured patients, ED mild traumatic brain injury patients demonstrated subtle but discernible neurocognitive deficits.