Immunotherapy has been used for over 80 years. It is a safe and effective therapeutic intervention for allergic rhinitis, but its use in the treatment of asthma is more controversial. Patients with unstable asthma are at increased risk of adverse effects from immunotherapy; therefore, if immunotherapy is used in such patients, it should be instituted cautiously. Indications for immunotherapy include evidence of IgE-mediated disease and positive results on skin tests or radioallergosorbent test (RAST). In addition, before immunotherapy is considered, measures to avoid exposure to offending agents and drug therapy should have failed to provide relief of symptoms. Before administering immunotherapy in the office, physicians should be knowledgeable about the use of immunotherapy and the treatment of anaphylaxis, and should have ready access to the equipment needed to avert anaphylaxis.