The moss Pohlia flexuosa was obtained as the protonema from its matured capsules. It was grown by shaking in modified Murashige-Skoog＇s medium, and the dry weight obtained was 40 mg per 20 ml medium after 15 d. The mature protonema removed Hg2+ from aqueous solutions. The higher the initial Hg2+ concentration, the higher the amount of Hg2+ removed, and the concentration factor, which is an indicator of the ability to remove heavy metals, was 2000 ml/g of dry moss at 50 mu g/ml of HgCl2. The optimal pH and temperature for Hg2+ removal were 7.0 and 25 degrees C, respectively. Sodium azide and dinitrophenol at 0.1 mM inhibited Hg2+ removal up to a relative removal of 81 and 77%, respectively. The importance of two processes, bioaccumulation and adsorption, in the removal of Hg2+ by this moss is discussed.