Multiple sclerosis (MS) onset is usually in adult life (age 20-40 years). Discordant data have been reported concerning the frequency of early onset MS (EOMS) that ranges from 2.7% to 5%, whereas there is a general agreement on prevalence of female sex, particularly after puberty. The initial symptoms in EOMS are frequently characterized by visual loss whereas the other functional systems are involved with a variable frequency. Literature data show that EOMS tends to have a relapsing-remitting course, a high rate of recovery from the initial attack, a long time interval between the first and second attacks and a slow progression rate. A poor prognosis is reported in a few cases of EOMS and seems to be related to number of relapses and to the delay between the first and second attacks.