The paper describes how absolute values of pollen deposition may be calculated from the results of volumetric sampling, supplemented by routine meteorological data. Daily mean values of concentration of birch pollen in the air at Lerwick, Shetland in 1970 and 1971 are presented, and these are used to calculate daily and annual depositions. The results are consistent with what is known about the occurrence of tree pollen in fossil and recent deposits in Shetland. [ABSTRACT FROM AUTHOR]