A two year study of the metal content of birch leaves shows that most of the major elements increase in content during the growth season, whereas Cu and Ni decrease during its beginning. All trace elements have rather constant contents after the beginning of July. Ground water changes seem to explain the differences in major element contents between samples taken from 1977 and 1978. Physiological and leaf weight changes could explain the major variations during the growth season and the physiologically influenced increases are well eliminated by normalizations. Only the 1977 Mn increase is not eliminated, probably because of unusual ground water content. The best normalizations found are those with respect to Fe + Al + Zn, Ba + Sr and Al + Ti. Irregular variations in metal contents are hardly caused by occasional weather changes; probably they are caused by occasional ground water variations.