Phytochemical investigation of the stem of Bruguiera gymnorrhiza yielded three new ent-kaurane diterpenoids (1, 2, and 3) and one new ent-beyerane diterpenoid (4) together with nine known ent-kaurane diterpenoids. All structures and the relative stereochemistry of the new compounds were determined by NMR spectroscopic studies. The absolute stereochemistry of 4 was determined by CD data. Some of the compounds showed moderate cytotoxic properties.