A method for delaying the onset of clinically definite multiple sclerosis in a patient at risk of developing clinically definite multiple sclerosis and retard long-term progression of multiple sclerosis and its symptoms, the method comprising periodically administering a pharmaceutical composition comprising a therapeutically effective amount of glatiramer acetate to the patient, thereby delaying onset of clinically definite multiple sclerosis in the patient and retarding long-term progression of multiple sclerosis and its symptoms.