We treated five consecutive patients with multifocal motor neuropathy (MMN) with high-dose intravenous immunoglobulin (IVIg). Four patients had increased levels of anti-asialo-GM1 IgM and two of anti-GM1 IgM as well; one patient had no reactivity. We treated them twice with 0.4 g/kg IVIg for 5 consecutive days at a 2-month interval, followed by maintenance infusions up to 6 to 12 months. All patients with high anti-asialo-GM1 had a consistent clinical improvement starting 3 to 10 days after the first IVIg course; in one patient, recovery was complete and persistent for 12 months without additional treatment, while in three patients, improvement only lasted 20 to 30 days. There was a similar improvement in these patients after the second course of IVIg which was maintained by periodic 2-day IVIg infusions. Clinical improvement in these patients was associated with a reduction of conduction block in most, but not all, motor nerves, while antibody titers were not consistently modified by treatment. There was no clinical or electrophysiologic improvement in the patient without antiglycolipid activity after 6 months of IVIg. IVIg may be a safe and effective therapy for MMN.