Recent insights regarding the development of allergic diseases such as allergic rhinitis, asthma and atopic eczema are based on the functional diversity of T helper (Th)1 and Th2 lymphocytes. Th2 cells (secreting Interleukin (IL)-4, IL-5, IL-9 and IL-13) are considered to be responsible for the induction and for many of the manifestations of atopic diseases. Local overproduction of Th2 cytokines at the site of allergic inflammation, and an intrinsic defect in the production of IFN-γ by Th1 cells in atopic individuals, have now been reported by several authors. Both IFN-γ and IL-10 have been suggested to play a modulatory role in the induction and maintenance of allergen-specific tolerance in healthy individuals. However, recent studies indicate that Th1 cells, secreting IFN-γ, might cause severe airway inflammation. On the other hand, ‘inflammatory T cells’ or Th17 cells, producing IL-17, could represent a link between T cell inflammation and granulocytic influx as observed in allergic airway inflammation. We focus in this review on local (at the side of inflammation) T cell cytokine production and cytokine production by circulating T cells (after in vitro restimulation) from individuals with allergic airway disease, rhinitis and/or asthma. We furthermore review the changes in local T cell cytokine production and/or cytokine production by circulating T cells (after restimulation in vitro) from allergic/asthmatic individuals after treatment with anti-inflammatory agents or immunotherapy. Finally, we discuss whether measuring these T cell cytokines in the airways might be of diagnostic importance or could help to follow-up patients with allergy/asthma.