The objective of this current meta-analysis is to determine whether IFN beta-1b is substantially better than other immunomodulating, immunosuppressive or anti-inflammatory drugs in modifying the clinical course of relapsing-remitting and secondary progressive multiple sclerosis (RR MS, SP MS). A comparison shows that in 2-year treatment IFN beta-1b, beta-1a s.c., glatiramer acetate, immunoglobulin G i.v. and mitoxantrone i.v. reduced annual relapse rate (45%), increased the proportion of relapse-free patients (34%), decreased the mean level of disability (-0.23 in EDSS) and diminished the fraction of RR MS patients with sustained progression (25%); p < or = 0.05. Azathioprine demonstrated considerable delay in the onset of action and loss of efficacy in the third year of treatment. IFN beta-1b and cyclical pulses of intravenous high dose methylprednisolone decreased the annual relapse rate and slowed the progression in SP MS patients; p < or = 0.04. All drugs significantly reduced the number of new and enlarging brain lesions on GdT1 and PD/T2 images in MRI (mean -68%). Furthermore, IFN beta-1b s.c. and beta-1a s.c. evidently reversed burden of the disease (BOD) on T2 images (median -4.7%); p = 0.001. However, glatiramer acetate, immunoglobulin G i.v., IFN beta-1a i.m., methylprednisolone i.m. and possibly azathiopirine failed to diminish BOD on T2 images; p = ns. It is concluded that in most RR MS patients IFN beta-1b has similar clinical effect to other immunomodulating drugs and mitoxantrone.