Objective: To investigate the characteristics and related influencing factors of cognitive impairment in patients with multiple sclerosis, and study the effect of cognitive impairment on their living function. Data sources: A computer-based online search of Medline database was undertaken to identify articles about the cognitive function of patients with multiple sclerosis published in English from January 2000 to December 2004 by using the keywords of "multiple sclerosis, cognitive function or neuropsychology", the subjects were human. Chinese relevant articles published between January 2000 and December 2004 were searched in Chinese journals full-text database, the keywords were "multiple sclerosis, cognitive function". Study selection: Preliminary check was implemented. The articles about the characteristics of cognitive impairment, its related influencing factors, and its correlation with living function in patients with multiple sclerosis were selected, and studies about the etiology and pathology of multiple sclerosis were screened. The full-texts of the rest articles were scanned, and the contents were analyzed and summarized. Data extraction: Totally 259 English literatures were collected, including 201 investigative articles and 58 reviews, 30 of them accorded with the inclusive criteria. Three Chinese articles were collected, and none was included. Data synthesis: The incidence rate of cognitive dysfunction in patients with multiple sclerosis of different forms and different severity was 45%-65%. The occurrence and severity had no obvious correlation with the disabled status of body. The patients with multiple sclerosis had obvious impairments in recent memory, attention, speed of information processing, ability of visual space and performance function, and their general intellectual level and language ability were reserved relatively, their cognitive dysfunction was associated with the decrease of the living ability. The cognitive dysfunction of multiple sclerosis was mainly detected with neuropsychological methods. Conclusion: The patients with multiple sclerosis have obvious impairments in recent memory, speed of information processing and performance function, and their general intellectual level and language ability are reserved relatively. Cognitive dysfunction can negative effects on the patients' living function.