By means of a Burkard Seven Day Recording Volumetric Spore Trap located in central Stockhom, about 20 m above ground level, pollen was sampled between March and August for eight consecutive years (1973–1980). The pollen spectra with special reference to trees, in particularBetulaandPinus, were compared as to amount and distribution of taxa. No co-variation between the two latter genera was noted.Betulashowed a ± distinct biennial periodicity. The main pollen season is defined.BetulaandPinusshowed slightly different patterns regarding beginning and duration of the pollen season; mean intensity is compared.