Allergic rhinitis is now considered an inflammatory disorder where many leukocyte types, including eosinophils and T-lymphocytes, accumulate in increased numbers. Along with mast cells and other cells, they release a wide variety of mediators, cytokines, and granule constituents that can directly cause inflammation or activate the local vascular endothelium to further enhance the recruitment of leukocytes through the expression and function of adhesion molecules. While the understanding of the importance of leukocyte and endothelial adhesion molecules is still at a very early stage, recent evidence has already begun to implicate these cell surface molecules in the pathogenesis of allergic diseases such as rhinitis and asthma. Additional studies, including the use of adhesion molecule antagonists when available, will clarify the importance of these structures in the pathophysiology of these disorders.