The release of pollen into the air is a normal part of the sexual cycle in many windpollinated plants. Unfortunately, however, certain pollen grains contain specific proteins or glycoproteins that can result in the familiar debilitating symptoms of hayfever and asthma in humans. This, together with the dramatic increase in the incidence of allergic disease in recent years, has led to increasing public concern about allergenic pollen. It is important to examine the distribution of pollen in the air, the particular molecular features of the allergens, and, perhaps most intriguingly, what role these highly interactive molecules play in pollen growth and development.