Multiple sclerosis (MS) is a chronic demyelinating disease of the central nervous system. The majority of MS patients have a relapsing-remitting course with progressive neurological disability that accumulates over the years. Intravenous Immunoglobulin (IVIg) has demonstrated benefit in the treatment of some patients with relapsing-remitting MS. Concerns about adverse events of IVIg, mainly acute renal failure and thromboembolic events have been raised in the medical literature. We examined the adverse events profile of IVIg treatment in a large cohort of 293 relapsing-remitting MS patients treated with an initial loading dose of IVIg (0.4 g/Kg body weight/day, for 5 consecutive days) and additional booster dose infusions (0.4 g/Kg body weight/booster dose, every 6 weeks) as a maintenance treatment. A total of 9281 IVIg infusions were administered within a mean treatment period of 3.8 +/- 3.5 years (3 months-10 years). The main adverse event during the loading dose period was headache, occurring in 12.6% of the patients. The annual rate of any adverse event during the IVIg maintenance period was 4.4% during the first year and had a trend to decrease with every passing year of treatment. Adverse events during the loading dose did not predict adverse events during the maintenance phase. No severe adverse events were recorded. We conclude that IVIg is a safe therapy in MS either for short or for long-term periods.