We assessed cognitive performance and physical disability in 111 multiple sclerosis (MS) patients and 222 healthy controls in a multicenter study in Argentina to obtain the prevalence of cognitive impairment (CI) in a population of MS outpatients in Argentina. MS patients presented significantly lower scores in all Brief Repeatable Battery of Neuropsychology (BRB-N) tests than did the control group. The prevalence of CI was 43.2%. This study allowed us to obtain actual figures on the number of MS patients with CI in a Latin American sample. This validation is a very useful tool for clinical practice and for research studies to assess cognition in MS.