Dissertation submitted to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree Master of Science. 2013 / The Babinski sign is a pathological response elicited by a stimulus to the lateral plantar border of thesole of the foot. The resulting reflex involves dorsiflexion (upward motion) of the toes, most notably the hallux, with accompanying flexion in the ankle, knee and hip. It is an important part of the clinical neurological examination and aids in the diagnosis of central nervous system dysfunction. There is however no wholly standardised method to elicit this reflex or interpret it, resulting in possible variation in its utility. The resulting aim of the studies constituting this dissertation were therefore to: 1) assess what techniques and pressures are used to elicit the reflex in a group of neurologists;2) to investigate the relationship between input variables of the reflex and the resultant output variables as measured with the use of electromyography and kinematics;3) compare objective variables, relating to toe, foot and leg movement, of the pathological reflex to the healthy response; 4) assess the inter-rater reliability of the reflex and 5) determine what aspects of the reflex are most closely related to the ratings of the students and neurologists. A specialized custom-built Babinski hammer was constructed to measure the duration of the stroke and pressures exerted on the foot of a single healthy subject by neurologists (n=12). The relationship between the recorded pressures and the movement of the toes (measured kinematically), muscle activity in the tibialis anterior and the pain felt by the subject (gauged using a visual analogue scale) were evaluated. Following this, the average pressure used by the neurologists was used to elicit the reflex in six patients with known positive Babinski responses and six healthy gender and age matched controls. These reflexes were compared with kinematic (measurement of toe, foot and leg movement) and electromyographic (muscle activity of the involved muscles) methods. These reflexes were recorded and the recorded footage was shown to 12 medical students and 12 neurologists who were asked to interpret if 3 the responses were pathological or non-pathological. Kinematic and electromyographic descriptions of each reflex made it possible to assess what aspects of the reflex are important for classification of a pathological response for both medical students and neurologists. A large amount of intra- and inter-rater variability was shown amongst the neurologists in how they elicited the reflex. The amount of pressure applied was shown to be significantly related to hallux movement (p<0.01) as well as to the degree of pain felt by the subject (p<0.01). Significant differences were found between the patients and controls for change in hallux angle (p<0.0001), movement latency (p<0.05)and the maximum electromyographic amplitude of tibialis anterior(p<0.01). The inter-rater reliability of the medical students and the neurologists showed substantial agreement between raters (kappa = 0.67 and 0.72 respectively). Both neurologists and students made use of the change in hallux angle, time taken to reach maximum ankle angle, movement latency and the maximum amplitude of gastrocnemius when rating the reflex. Neurologists alone observed time taken to reach maximum hallux angle and change in ankle angle as being important while medical students‘ alone looked at maximum amplitude of biceps femoris. In conclusion, I found a large variation between the techniques of neurologists when assessing the Babinski reflex. This variation is related to variation in aspects of the resultant reflex. The pathological response (the Babinski sign) has shorter movement latency and less activity in the tibialis anterior muscle than the flexor response seen in healthy individuals. Ratings of pre-recorded Babinski responses had substantial agreement when both neurologists and medical students assessed pathology. In order to assess them both groups made use of the speed of the reflex, the direction of hallux movement and concurrent withdrawal activity in the leg to differentiate between a pathological and a healthy response.