Fucus vesiculosus was extd. with supercrit. CO2 at 50 degrees C under 300 bar and analyzed for content of fucosterol by supercrit. fluid chromatog. with photodiode array detector. The anal, method was validated by using a fucosterol std. The extrn. yield was 2.83% and the fucosterol content in the extract was 8.06% by mass.