An epidemiologic and clinical study on optic neuritis in two sanitary districts of the Sardinia was carried out. The results were partially in agreement, partially in contrast with the literature data. The most important datum is that the annual incidence rate of optic neuritis in Sardinia is similar to the rates observed in medium-high risk for MS geographical areas, according to observation which showed that frequency of MS in Italy, and in Sardinia particularly, is much higher than that indicated by previous studies.