The purpose of this study is to show the dose-response relationship of three doses of mitoxantrone with regard to efficacy in patients with secondary progressive multiple sclerosis and to show the safety and tolerability of mitoxantrone in these patients.

Inclusion Criteria:

• Secondary progressive MS in an active stage
• EDSS between 3 and 6

Exclusion Criteria:

• Benign or primary progressive MS
• Patients with cardiac risk factors
• Patients who have already received mitoxantrone