Chlorinated guaiacols (4,5,6-trichloro-,4,5-dichloro-, and 4-chloro-guaiacol) at 0.2 mM were completely degraded by anaerobic digester sludge within 4 d, but complete removal of TeCG could not be attained. The removal rates of chlorinated guaiacols by adsorption and biodegradation were in the following order: 4,5-dichloroguaiacol > 4-chloroguaiacol = 4,5,6- trichloroguaiacol > tetrachloroguaiacol. The most rapid initial TeCG degradation occurred in the glucose-supplemented cultures. However, the degradation rate of 4, 5,6-TriCG was not increased significantly by supplementary glucose.