Heart Rate Variability (HRV) reflects the responsiveness of the autonomic system to an external stimuli. The aim of this system is to maintain homeostasis.The variability implies on the interaction between the sympathetic and the parasympathetic systems to maintain the ongoing changes of the autonomic system. Following Acquired Brain Injury (ABI), there can be a damage to the Central Nervous System (CNS) function. The damages described in the literature are cognitive, motor and behavioural function, while there is less relation to the autonomic system. The autonomic system can influence the ability of patient with ABI to participate in the rehabilitation program. The aim of this work is to investigate the activity of the autonomic system activity as manifested by HRV among patients with ABI in different conditions: resting, during activity and while listening to different auditory stimuli.