Growing awareness and accumulating data regarding the cognitive impairment and its progression in multiple sclerosis (MS) patients has received an important place in neurological research in the last decade. Cognitive impairments occur frequently (43 to 65%) in MS. Moreover, in up to 50% of patients in whom no cognitive disturbances are found on routine neurological examination, cognitive impairments can be elicited using sensitive and disease specific neuropsychological tests. Even in patients with short disease duration of less than two years, discrete impairment of cognitive function may be found in up to 60% on neuropsychological testing without impacting activities of daily living.