Vaccinations to prevent communicable diseases are, like in other chronic diseases, of special importance in patients with multiple sclerosis (MS). Various bacterial and viral infections have been shown to induce relapses of MS. Reports of possible adverse effects of vaccinations on the course of multiple sclerosis have led patients and treating physicians to exercise caution in the use of vaccines. A number of vaccines have been studied with respect to the risk in MS patients. Some vaccines, for example against yellow fever, are not indicated in MS due to the risk of MS exacerbation. In contrast, tetanus or hepatitis B vaccines do not represent a risk for manifestation or disease progression of MS. Before and during immunomodulatory therapy of MS special attention should be given to adequate protection against vaccine preventable diseases.This paper reviews the indications and specific side effects of vaccinations in MS patients. Additionally, issues of vaccination under immunomodulatory therapy of MS are discussed.