The objectives of this study were to: (1) demonstrate the use of computerized, three-dimensional gait analysis as a functional assessment instrument following clinical intervention; and (2) objectively quantify the effects of focal muscle denervation via botulinum toxin type A (BTXA) injection in a hemiparetic patient with lower extremity spasticity following traumatic brain injury (TBI). A desired outcome of this intervention was to realize kinematics more closely resembling those reported for normal patients. The design was a single-subject case study. Ten trials of walking gait were analysed pre-injection (PI), 1 week post-injection (1PO) and 4 weeks post-injection (4PO). The PI and 1PO sessions were found to be appreciably different from the 4PO on the joint angles of the ankle and knee at each phase of the gait cycle. These differences resulted in a reduced asymmetry of ambulation. Stride time, stance time, percentage stance time, percentage swing time and walking speed improved, showing progress towards a more efficient gait pattern. Decreased stride time and increased walking speed supported improved functional ability. The inter-trial variability of the gait parameters showed the analysis to be a consistently reproducible protocol. Conclusions based on the results included encouraging findings for the efficacy of botulinum toxin A as a therapy for the reduction of spasticity.