Few studies have reported the use of supercritical fluids as solvents in dyeing of textile fibers. Studies on synthesis of new dyestuff that can be used in this technique and their solubility in the supercritical fluid are attracting increasing attention. In this study, wool fibers were dyed with mordant dyes dissolved in supercritical carbon dioxide. We used three mordant dyes that have chelating ligand properties, 2-nitroso-1-naphthol (C.I. Mordant Brown), 5-(4-aminophenylazo) salicylic acid (C.I. Mordant Yellow 12) and 1,2-dihydroxyanthraquinone (C.I. Mordant Red 11 also called Alizarin) which were dissolved in supercritical carbon dioxide, and five different mordanting metal ions, Cr(III), AI(III), Fe(II), Cu(II) and Sn(II). Wool fibers were mordanted by the metal using conventional techniques and dyed at 333-353 K temperature and at 150-230 atm pressure. Dyed materials had excellent wash fastness properties. (C) 2000 Elsevier Science B.V. All rights reserved.