The adsorption of two basic dyes, methylene blue and Astrazone red violet 3R on the moss, Calymperes delessertii Besch, was studied. The parameters studied included contact time, particle size and dose of absorbent, initial concentration and pH of dye solution and temperature. The results indicate that the moss is an efficient adsorbent and the rate determining factor is probably a combination of surface adsorption and diffusion within the moss.