The division of T cells into distinct subsets (Th-1 and Th-2), based upon cytokine production, is a major advance in understanding the immune reactivities particularly those associated with allergy. This report summarizes some of the highlights on pathogenesis of allergic rhinitis. Th-2 cells, driven by IL-4, play an important role in allergic reactions inducing IgE switching in B cells and proliferation of mastocytes. In addition, by interaction with IL-5, Th-2 lymphocytes promotes eosinophil growth. By contrast, Th-1 cells antagonize Th-2 activity by IFN-gamma production. Finally IL-10, produced by Th-2, blocks the effects of the cytokines elaborated by Th-1. Recent results of this rapidly expanding area of research provide the background for this review. The intricate connections between Th-1, Th-2, the endothelial cells of the nose vessels and stromal cells are discussed.