Chlorinated compounds constitute an important class of xenobiotics. Crude laccase was produced using Trametes versicolor ATCC (200801) in potato dextrose broth, with wheat bran as an inducing medium, and its ability to dechlorinate eight compounds was determined. The compounds were 2-chlorophenol, 4-chlorophenol, 2,4-dichlorophenol, 2,6-dichlorophenol, 2,4,5-trichlorophenol, 2,4,6-trichlorophenol, heptachlor and pentachlorophenol. A range of parameters for the dechlorination of some compounds was tested, including incubation period, pH, initial substrate concentration, temperature, and enzyme quantity. The oxygen consumption was determined during each dechlorination process, under pre-determined optimum conditions. The changes in chemical structure of the compounds were also determined, by using FTIR analysis, following dechlorination of test chlorophenolics. Strong interactions were found to lead to the reactivity of hydroxyl groups in some cases and chlorine atoms were released from the benzene ring. The changes in compound toxicity were monitored before and after enzymatic treatment, using Microtox. Quantitative structure-activity relationships for the toxicity of the chlorinated compounds were developed. Consequently, the toxic activity of the test compounds was controlled by electrophilic index and electronic properties.