This invention provides a method of treating a patient afflicted with multiple sclerosis or presenting a clinically isolated syndrome comprising administering to the patient laquinimod as an add-on therapy to or in combination with interferon-β. This invention also provides a package and a pharmaceutical composition comprising laquinimod and interferon-β for treating a patient afflicted with multiple sclerosis or presenting a clinically isolated syndrome. This invention also provides laquinimod for use as an add-on therapy or in combination with interferon-β in treating a patient afflicted with multiple sclerosis or presenting a clinically isolated syndrome. This invention further provides use of laquinimod and interferon-β in the preparation of a combination for treating a patient afflicted with multiple sclerosis or presenting a clinically isolated syndrome.