Few studies have addressed whether there are differences in clinical efficacy between intravenous methylprednisolone (methyl-Pd) and intravenous immunoglobulin (IVIg) use. We retrospectively compared platelet responses and toxicities associated with these two treatments in adult patients with immune thrombocytopenia. Patients received intravenous methyl-Pd therapy followed by oral prednisolone (Pd) from 1993 to 2002 and IVIg together with oral Pd from 2003 to 2008. Early response and maintenance of the response were assessed at 7 days and 6 months after treatment, respectively. Of the 87 patients enrolled, 77 (88.5%) were eligible for analysis. Early responses occurred in 30 of 39 patients (76.9%) receiving methyl-Pd versus 33 of 38 patients (86.6%) receiving IVIg (p = 0.187). The response was maintained in 28 patients (71.8%) in the methyl-Pd arm and in 23 patients (60.5%) in the IVIg arm (p = 0.187). The time to a complete response in the IVIg arm (6 days; range, 1 to 35) was shorter than that in the methyl-Pd arm (13.5 days; range, 2 to 29) (p = 0.002). Side effects were mild and tolerable in both arms. Five years after initiating treatment, 7 of 18 patients (38.9%) and five of 14 patients (35.7%) were still maintaining a response in the methyl-Pd and IVIg arms, respectively. These results indicate that neither the early response rate nor the long-term outcome differed between the methyl-Pd and IVIg treatments. However, IVIg induced a complete response more rapidly than did methyl-Pd.