There are several reports that Guillain-Barre syndrome (GBS) is closely associated with immunologic disturbance, although the exact mechanism of GBS is not fully understood. Recently intravenous human immunoglobulin (IVIg) has been implicated to improve clinical course of several immune-mediated diseases, which are resistant to conventional therapy. Authors studied retrospectively the effectiveness of IVIg therapy in GBS and compared the clinical courses in this group with those of control GBS group without IVIg therapy or plasmapheresis. Ten subjects with GBS were treated with IVIg. IVIg of 0.4gm/kg/day was slowly infused via parenteral route for five days as one schedule. At the time of infusion, the status of GBS were regarded as moderate to severe. All GBS subjects showed arrest of progression and began to improve at longest from the third day of IVIg therapy. The intervals from the day of maximal neurologic disability score (NDS) to the day of 30%-decrease of maximal NDS were estimated as 10+6 days and 22+11 days, respectively in IVIg-treated and in control GBS group, which showed significant difference(p<0.05). One patient who had been in maximal neurologic deficit 8 days prior to therapy showed very poor response to IVIg therapy. Another patient showed initial improvement after the first cycle IVIg therapy, and subsequently showed relapse on the 6th day of therapy. So the second cycle of IVIg therapy was needed to arrest the down-hill course. Regarding side effects of IVIg, one patient experienced generalized itching sensation transiently without skin eruption. Another patient showed previously unreported severe neutropenia immediately after one cycle of IVIg therapy, which was normalized 2 weeks after stopping IVIg. We thought that IVIg therapy was effective and relatively safe to lessen neurologic deficit and to shorten clinical course during the period of acute or progressive stage of GBS.