Birch pollen concentrations recorded by volumetric sampling for a three year period on the rural Baltic island, Gotland, are presented and compared with the birch pollen records for the same period in Stockholm. Since the incidence of birch pollen allergy among the farmers on the island was found to be lower than on the mainland it was generally believed that the airborne birch pollen concentration on Gotland was relatively low. Although birch is only scattered on the island, theBetulapollen concentrations in the years investigated appear to be as high as or higher than those in Stockholm, where birch is one of the main elements of the urban vegetation. The reasons for the abundance of birch pollen in the air of Gotland in relation to the low figure of sensitisation to birch pollen are discussed.