Interferon Beta is well established as a first line agent to treat relapsing remitting Multiple Sclerosis. It frequently induces the formation of neutralising anti-Interferon Beta Antibodies (Nabs) which may abrogate the clinical efficacy of the drug. Numerous studies have shown a loss of bioactivity of the drug in the presence of Nabs. The focus has shifted to reliable quantification of Nabs and their appropriate incorporation into clinical practice. Here we review the development and persistence of Nabs, the effect on Interferon beta bioactivity, clinical and para-clinical autocome measures in trials, Nab assays and discuss management strategies to optimise the use of Interferon beta in relapsing remitting MS.