OBJECTIVE: To determine the effects of increasingly demanding environments related to simultaneous visual tasks and physical obstructions on the locomotor ability of people with traumatic brain injury (TBI). DESIGN: Group comparison study. SETTING: Gait analysis laboratory within a postacute rehabilitation facility. PARTICIPANTS: Volunteer sample of 9 people (8 men, 1 woman; age, 39.3+/-13.0y) with moderate to severe TBI and a comparison group of 9 subjects without neurologic problems matched for age and sex (8 men, 1 woman; age, 39.7+/-12.3y). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Reading times for the Stroop bar and Stroop word tasks, walking speeds, stride lengths, and obstacle clearance margin. RESULTS: The TBI group was slower than the control group in performing the Stroop bar task during sitting (P=.002), and while avoiding the narrow obstacle (P=.05), and in performing the Stroop word task while avoiding the wide obstacle (P=.019). Despite their relatively normal gait speeds on level ground, subjects with TBI walked more slowly than control subjects for the narrow (P=.024) and the wide (P=.019) obstacle conditions and for the most complex dual task (P=.042). Greater lead-limb clearance margins were observed for the TBI group than for control subjects for all conditions whereas no differences were found for the trail limb except at the far end of the wide obstacle. CONCLUSIONS: Despite their good recovery of locomotor function, with respect to normal level walking speeds and ability to avoid obstacles, subjects with moderate and severe TBI showed residual deficits in relation to greater difficulties in dealing with environments that challenge their locomotor and attentional abilities. The use of such naturally based dual tasks may help identify some of the environmental obstructions to social participation after TBI.