Morphophysiological parameters of pollen (pollen grain size, pollen tube length, viability, fertility) were investigated in Betula pubescens Ehrh., B. pendula Roth, B. pendula Roth var. carelica (Mercklin) Hamet-Ahti, В. папа L., representing East Fennoscandian native wood flora, and in introduced species - B. ermanii Cham, and B. japonica Sieb. It is shown that the range of variation of pollen fertility and pollen grain size mainly depends on distinctive features of the species, whereas that of viability and pollen tube length - on variations within species. Expression of male gametophyte traits is thought to be related to the adaptive response of some species to natural and climatic conditions. Thus, low pollen fertility in B. pendula and B. ermanii is compensated by its high viability and development of elongated pollen tubes. B. pubescens has high pollen fertility, but low percent of germination and small length of pollen tubes. В. папа has small pollen grains, but quite high values of fertility, viability and pollen tube length, which enable the species' successful growth in wetland habitats. The quality of B. penduia Roth var. carelica (Mercklin) Hamet-Ahti pollen proved to be lower than in other species, which is, alongside with other factors, a possible reason for its narrow distribution range. The best pollen qualities during the study period were demonstrated by B. japonica Sieb. - a species introduced in Eastern Fennoscandia.