IVIG is of value in patients with primary and secondary antibody deficiencies. High dose IVIG therapy is usually the treatment of choice for patients with primary antibody deficiency disease. Sufficient IVIG should be given to maintain IgG trough levels of > 500 mg/dl; this usually requires a dose of 400 to 500 mg/kg/month. Adverse side effects to IVIG has been described; the two most common serious side effects are hepatitis C and aseptic meningitis. New procedures to inactivate hepatitis C (and other viruses) are now in place. Aseptic meningitis is usually associated with high IVIG doses given rapidly to patients with autoimmune and inflammatory disease; its cause is not known. Subcutaneous infusions of IG or IVIG at weekly intervals has been shown to be clinically efficacious, well-tolerated and a less expensive alternative to monthly IVIG infusions. IVIG has been used with encouraging results in selected pediatric patients with HIV infection. The benefit is primarily in patients with CD4 counts > 200 cells/mm2 who receive no P. carinii pneumonia prophylaxis. IVIG may also be of value in preventing or ameliorating infection in other secondary antibody deficiencies including patients with malignancies; patients with protein-losing enteropathy and nephrotic syndrome; severely ill care patients with shock, trauma or surgery; premature infants and patients undergoing transplantation procedures; and severely burned patients. Guidelines for selecting patients for IVIG are offered.