Wool samples containing various anionic surfactants (alkylbenzene sulphonates, primary and secondary alkane sulphonates, and an olefin sulphonate) lose some of the surfactant to the treatment liquor when subjected to typical dyeing conditions. At the boil, equilibrium is set up within 15 minutes between the concentration of surfactant in the liquor and that on the fiber. The extent of extraction is influenced by the alkyl chain length of the surfactant, the pH of the liquor, and the bath volume. For many surfactants, less than 5% is extracted at a 20:1 liquor/wool ratio in the pH range 5-6. The presence of nonionic surfactant in the treatment liquors results in slightly higher levels of extraction. Exhaustion of anionic surfactants onto wool gives distributions of surfactant between the wool and liquor similar to those obtained when treated wools are extracted under the same conditions of temperature, pH, and liquor / wool ratio.