Clinical characteristics of multiple sclerosis with early onset are described. The evolution is frequently relapsing-remitting; compared to the adult form, the EDSS levels of 3, 4 and 6 are reached after a longer interval but at a lower age. Negative prognostic factors are: a short inter-attack interval, a high relapse rate, a relapsing-progressive course or the shift to the secondary progressive phase, and early accumulation of disability.