Globally, the course and prognosis of multiple sclerosis are heterogeneous, and generally considered to be unpredictable. Advances in statistical techniques have made it possible to analyze representative cohorts of patients to clearly delineate the overall prognosis of the disease, beyond individual variations. For each individual however, there appears to be a steady progression as shown by serial quantified neurological examinations. At the present time early prediction of outcome remains impossible. In the near future, new imaging techniques may provide a solution to this problem allowing selection of patients at risk who could benefit from early treatment.