The aim is to describe and discuss the ongoing debate on how to balance an increase in clinical efficacy against a heightened risk of developing serious side-effects, as has surfaced recently with some novel therapies for relapsing forms of multiple sclerosis.New therapies are emerging that differ with regard to their mechanism of action, their mode of administration, their side-effect profile and the clinical benefits that they offer to patients in comparison with established therapeutic modalities in multiple sclerosis. Treating physicians will need to make choices on the best treatments for their patients on the basis of limited experience. This process requires optimal assessment of risks and benefits.Careful assessment of the risk-benefit profile of the various options may allow treatment choices and perhaps ensure that patients obtain the most benefit from treatment without being exposed to unnecessary risk.