The use of immune globulin intravenous (IGIV) as replacement therapy in immunodeficiency disease and as anti-inflammatory or immunomodulatory therapy in a variety of autoimmune and inflammatory diseases has expanded dramatically over the last decade. With this expansion, new challenges and concerns have emerged. As well, new products have been introduced while others have been discontinued. This evolution poses the important issue of product selection, choosing the "right" product for an individual patient. As the manufacturing process, virus reduction methods, and final formulation and composition differ widely among these products, it is intuitive that clinical outcomes, including both safety and efficacy, could also differ. This review examines such differences among currently available products in the United States and their potential to affect clinical outcomes.