This study was performed in order to verify the prevalence of retinal periphlebitis and other ocular changes in a well-defined population of multiple sclerosis (MS) patients, and to correlate the presence of these features with some clinical variables which characterize the disease. 110 MS-affected subjects were submitted to a standard ophthalmologic examination including a biomicroscopical evaluation of the fundus oculi. The prevalence of retinal sheathing in MS patients was found to be nearly 36%. It is significantly higher in patients evaluated in an active phase of the disease than in those examined in a stationary phase.