We studied the relationships between magnetic resonance imaging (MRI) and the Luria-Nebraska Neuropsychological Battery (LNNB) in 64 patients with relapsing-remitting multiple sclerosis (MS). MRI films were scored according to arbitrary descriptive criteria designed to emphasize patterns of alterations. Five groups were created: group 1 and 2 had typical discrete white matter lesions, group 3 had confluent lesions, group 4 had large discrete lesions and group 5 had only few small lesions. In addition, groups 2 and 3 had evidence of parenchymal atrophy. Groups 2 and 3 were the most impaired on the LNNB, but none of these patients was actually demented. Groups 1 and 5 were globally intact in spite of very different mean age and MRI pattern. Group 4 was composed of younger subjects with a shorter disease duration; they showed mild loss of attentive and abstracting abilities. We suggest that since their MRI was showing greater signs of local biological activity their mental deficits may be a transitory condition capable of two distinct outcomes: a favorable one as in groups 1 and 5, and a slowly progressive one associated with loss of brain tissue as in groups 2 and 3.