Study to Compare Double-dose Betaferon to the Approved Dose, for Patients With Early Secondary Progressive Multiple Sclerosis (SPMS)

Inclusion Criteria: * Diagnosis of MS for no less than one year and no longer than ten years * Disease in the secondary progressive (SP) phase * At least one relapse the last 3 years * Treatment with an interferon for at least 6 months and with Betaferon for at least 3 months Exclusion Criteria: * Serious or acute heart disease * Severe depression * Serious or acute liver, kidney or bone marrow dysfunction * Epilepsy not adequately treated * Pregnancy or lactation * Alcohol or drug abuse