Neurofibromatosis (NF) type I is a common autosomal dominant disease that principally affects the skin and peripheral nervous system. Neurofibromatosis type I associated multiple sclerosis is a very rare condition. A 28-year old NF1 man developed progressive spastic-ataxic gait, left side dysmetria, right internuclear ophthalmoplegia, spastic dysarthria. MRI of the brain depicted Dawson finger appearance demyelination of the corpus callosum and other multifoci demyelinating lesions typical for MS. CSF revealed high CSF protein with negative oligoclonal band. Visual evoked potential showed prolonged P100 latency, abnormal waveform and temporal dispersion bilaterally. The syndrome partially responded and stabilized with corticosteroid. Six months later progression of the syndrome characterized by paraparesis, bilateral cerebellar hemispheric syndrome and bilateral internuclear ophthalmoplegia occurred. Repeated MRI revealed more extensive white matter lesions extended into centrum semiovale. The progressive syndrome did not respond to corticosteroid. Primary progressive multiple sclerosis was diagnosed. Only thirteen cases with NF1 and multiple sclerosis have been described in the literature. The association has been hypothesized to be related to mutations in the neurofibromin protein or oligodendrocyte-myelin glycoprotein (OMgp) gene.