Multiple sclerosis (MS) is an immune-mediated disease of the central nervous system with a complex and heterogeneous pathology that may ultimately lead to neurodegeneration and brain atrophy. Brain volume loss in MS is known to occur early in the disease course and to be clinically relevant, as it has been related to disability progression. Nowadays, brain volume loss is relatively easy to measure with different automated, reproducible and accurate software tools. Therefore, most of (if not all) the newest clinical trials have incorporated brain volume outcomes as a measure of treatment effect. With this review, we aimed to update and summarize all existing data regarding brain volume and RRMS treatment in clinical trials as well as in open-label observational studies of drugs with positive results in its primary outcome in at least one phase III trial as of March 2014.