Passive immunization employs preformed antibodies provided to an individual that can prevent or treat infectious diseases. There are several situations in which passive immunization can be used: for persons with congenital or acquired immunodeficiency, prophylactic administration when there is a likelihood of exposure to a particular infection, or treatment of a disease state already acquired by the individual. Passive immunization is limited by short duration (typically weeks to months), variable response, and adverse reactions. This article focuses on specific immunoglobulins for preventing or treating infectious diseases, as these are the most likely scenarios one might encounter in primary care practice.