Multiple sclerosis is a cronical, inflammatory disorder of the brain and spinal cord in wich lymphocytic infiltration leads to damage of myelin and axons. MS is belived to be caused by a complex interplay between environmental factors as well as different genetic factors. Studies have demonstrated that approximately 30 % of the total risk is due to genetics. This review discusses some of the environmental factors suspected to play a role in MS. Vitamin D and sun exposure reduce the risk of MS. A diet rich in fish could have a protective role. Studies have suggested links between animal fat consumption and MS incidence.