Specific immunotherapy has been in routine use since 1911 for the treatment of respiratory allergic diseases. There is however a certain amount of controversies regarding its overall indications. Its efficacy has been demonstrated in double-blind placebo controlled studies in both allergic rhinoconjunctivitis and allergic asthma. The improvement of allergenic extracts (in particular by standardization), the better understanding of the mechanisms of action of immunotherapy, the recently proposed use of other administration routes and the publication of guidelines have legitimated its definite role to play in the therapeutic management of allergic respiratory diseases.