This invention provides a method for treating or for reducing ambulatory deterioration in a human patient diagnosed to be afflicted with relapsing-remitting multiple sclerosis (RRMS) and having a high baseline disability score according to the Kurtzke Expanded Disability Status Scale (EDSS), comprising periodically administering to only the patient diagnosed with RRMS and having a high baseline disability score an amount of laquinimod effective to treat the patient or to reduce ambulatory deterioration. This invention further provides pharmaceutical compositions and packages comprising an effective amount of laquinimod for treating a human patient diagnosed to be afflicted with RRMS and having a high baseline disability score according to the EDSS.