The exts. were analyzed by gas chromatog. to det. contents of sesquiterpenes, triterpenes, flavonoids, phenyl-propenoids and sterols. Significant differences in the chem. compn. of exts. from both birch species were obsd. Silver birch (Betula pendula Roth) and downy birch (Betula pubescens Ehrh.) twigs were disintegrated (grain size 0.5 mm), dried and extd. with supercrit. CO2 at 40 degrees C under 30 MPa for 3 h. The ext. yields were 8.4% and 4.8%, resp.