Observational studies have shown an association between lower vitamin D levels and higher risk of relapse among people with multiple sclerosis (MS). This has raised interest in potential clinical benefits of vitamin D supplementation in the management of MS. The objectives were to examine the effect of vitamin D based interventions on the relative risk of relapse in MS. Any randomised controlled trial assessing the effect on the relative risk of relapse of any formulation or dose of vitamin D, in participants with MS, was eligible. The inverse variance with random effects model in Review Manager 5.1 was used to calculate the odds ratio of relapses in high dose vitamin D treated patients vs. controls. Five studies were published as of September 2012, yielding a total of 129 high-dose vitamin D-treated patients and 125 controls. We found no significant association between high-dose vitamin D treatment and risk of MS relapse (OR 0.98, 95% CI 0.45-2.16). In conclusion, although no significant association between high-dose vitamin D treatment and risk of MS relapses was found, the studies were limited by several methodological limitations. Further larger, more prolonged studies are merited