Intravenous immunoglobulin (IVIg) has been used successfully for hypogammaglobulinemic states for more than 20 yr. In both primary and secondary situations when hypogammaglobulinemia is of clinical significance, IVIg should be the first line of treatment. In most cases, 400 mg/kg infused every 3 to 4 wk will lead to a trough level higher than 500 mg/dL, which in most cases provides good protection against bacterial infections. Higher doses may be needed in patients with known lung damage. Side effects include headache, nausea, chills, and fever but can be minimized by lowering the infusion speed rate. Rarely, aseptic meningitis may develop but it is always reversible. Although all products have been shown to be beneficial, differences among the various products have still been reported. In this regard, all products should be standardized according to common accepted international parameters. The route of immunoglobulin G replacement (intravenously vs subcutaneously) was reported to be of similar benefit. However, guidelines for usage and choice of route should be established and might be of help.