Immunoglobulin replacement therapy has been standard treatment in patients with primary immunodeficiency diseases for the past 3 decades. The goal of therapy is to reduce serious bacterial infections in individuals with antibody function defects. Approximately one-third of patients receiving intravenous immunoglobulin treatment experience adverse reactions. Recent advances in manufacturing processes have resulted in products that are safer and better tolerated. Self-infusion by the subcutaneous route has become popular and resulted in better quality of life. This review summarizes the use of immunoglobulin therapy in primary immunodeficiency diseases including its properties, dosing, adverse effects, and different routes of administration.