Human immune globulin administered intramuscularly has been used for more than 40 years. In the last decade intravenous preparations were developed. They do not aggregate and contain IgG molecules with intact recognition and effector functions. These compounds are safe and only minor side effects were reported even when high doses were given. The mechanism by which intravenous gammaglobulin exacts its function is a combination of the Fc receptor blockade in the reticuloendothelial system, a marked increase in the suppressor cell function with down regulation of the antibody production and an intervention in the idiotype-antiidiotype network. Human immune globulin is an important therapeutic tool not only in the antibody deficiency, but also as an immunomodulatory agent in autoimmune disorders.