In connection with our continuing studies of the constituents of the red algae of the genus Laurencia (Rhodomelaceae), a number of halo-chamigrene derivatives were isolated from the Japanese species of Laurencia. We describe herein the structures of several halo-chamigrene derivatives. Halogenated sesquiterpenes, 1,2,3,4,5 and 6, were isolated from L. glandulifera, the structures of which were determined on the basis of the chemical and spectroscopic evidence. The absolute configuration of 1 was established by X-ray crystallographic analysis. The absolute configurations of other compounds, 2,3,5 and 6, were confirmed by the spectral data and the chemical correlation with 1. Furthermore, the structure and the absolute configuration of spirolaurenone (14), possessing a spiro[4.5]decane skeleton, which was isolated from the same alga, were confirmed by the chemical correlation with glanduliferol (2). Halo-chamigrene derivatives, 16 and 17a,were isolated from L. majuscula together with a minor component,21. The structures of these compounds were determined by the chemical and spectral methods. The absolute configuration of 16 was established by X-ray analysis of the acetate (20) of 16. Several known halogenated chamigrene derivatives were also isolated from L. nipponica together with seco-chamigrenes.