Although intravenous immunoglobulin (IVIG) has primarily been recognized as useful in patients with antibody deficiencies, it continues to be used for an ever-expanding list of conditions. In addition to antibody replacement, IVIG may act as an immune modulator in certain autoimmune and inflammatory conditions. Its use should be carefully weighed against the high cost of the product. In conditions where it appears to be useful, controlled studies are necessary to prove its efficacy and its cost benefits.