Patients with mild traumatic brain injury (TBI) often complain of dizziness. However, these problems may be undetected by a clinical exam. Therefore, the purpose of this study was to evaluate the relationships between the subjective and objective measures of balance impairment. Ten patients with TBI (6 men and 4 women) and 10 matched controls participated in this study. Average duration since the TBI was 2.8 years (range 0.4-14.4). Six of the 10 subjects with TBI had abnormal imaging studies. All subjects and controls had a normal neuromuscular exam. Tinetti Balance Assessments were obtained and the TBI group was not significantly different from the control group. The Dizziness Handicap Inventory (DHI) score supported their complaints of "unsteadiness" and "imbalance" from the subjects with TBI. The DHI score was 32 +/- 23 (range 4-68) out of a maximum possible score of 100. Balance was tested using computerized dynamic posturography. The Sensory Organization Test score was significantly lower for subjects who had a TBI (70 +/- 12) compared to the control subjects (80 +/- 8), which indicated that the subjects with TBI had poorer balance than the control subjects. A 13-link biomechanical model of the human body was used to compute the kinematics of the whole body center of mass (COM) while walking on a level surface. The subjects with TBI had significantly less displacement in the anterior/posterior direction, walked significantly slower, had significantly greater medial/lateral sway and velocity than the normal controls, and had significantly greater medial/lateral imbalance. There was a significant relationship between the physical aspects of the DHI and posturography. There was also significant relationship between the physical, functional, and total DHI and the motion of the COM. Overall, the motion of the COM predicted between 42 and 69% of the DHI score. The present study has demonstrated that objective measurements can quantify the patient's functional deficits. Therefore, these objective measurement techniques should be used to assess the clinical complaints of imbalance from patients with TBI.