Dried leaves of Betula pendula Roth (14 batches) and B. pubescens Ehrh. (3 batches) present a similar flavonoid pattern. The mean levels of the principal flavonoid compounds were respectively: total flavonoids 3.29 and 2.77%, hyperoside 0.80 and 0.77%, avicularin (two forms) 0.57 and 0.26%,