Background: Severe pemphigus vulgaris (PV) is conventionally treated with high-dose oral prednisone, usually in combination with an immunosuppressive agent (ISA). Some patients experience significant side effects, which are sometimes fatal, from prolonged immunosuppression. Objective: Intravenous immunoglobulin (IVIg) was administered to 21 patients with severe cutaneous and mucosal PV who had not responded to the prolonged use of oral prednisone and multiple ISAs. Methods: A preliminary dose-determination study tested 7 additional volunteers to ascertain the optimal IVIg dose of 2 g/kg per cycle. Parameters to assess clinical outcome were recorded before and after IVIg therapy. Variables tested were highest dose, total dose, and duration of prednisone and ISAs, their side effects, frequency of recurrence and relapse, duration of IVIg therapy, clinical response, induction and duration of remission, number of hospitalizations, total days of hospital stay, and quality of life. Results: Use of IVIg monotherapy resulted in effective control of disease and produced a sustained remission in the 21 patients. The patients became free of lesions and remained so after finishing IVIg therapy. IVIg had a steroid-sparing effect and produced a high quality of life. Serious side effects from the use of IVIg were not observed. IVIg needs to be gradually withdrawn after achievement of clinical control. Conclusion: In patients with PV who do not respond to conventional immunosuppressants, IVIg appears to be an effective treatment alternative. Its early use is of significant benefit in patients who may experience life-threatening complications from immunosuppression. IVIg is effective as monotherapy. (J Am Acad Dermatol 2001;45:679-90.)