Immunotherapy is a controversial treatment for allergic diseases. However, controlled studies, either with a control group or as placebo-controlled double-blind trials, have documented a significant efficacy in Hymenoptera allergy, rhinitis and asthma. No strict scientific guidelines as to the use of immunotherapy can be provided. However, the 1993 Immunotherapy Position Paper of the European Academy of Allergology and Clinical Immunology recommended immunotherapy for patients with an unequivocal IgE-mediated disease who do not respond adequately to allergen avoidance and who require prophylactic topical corticosteroids for long periods. The clinical benefit, risk and potential preventive aspects of immunotherapy should be carefully assessed. Immunotherapy should as a routine only be initiated with allergens that have been shown in controlled studies to have clinical efficacy and safety. A treatment approach using immunotherapy as a supplement to pharmacotherapy is recommended, thereby interfering broadly with the pathophysiological mechanisms of allergic inflammation.