Chlorinated and nitroaromatic compounds are non-degradable substances that are extremely toxic and are known to be carcinogens and mutation causing agents. Moreover, the half-lives of substances such as carbon tetrachloride, hexachloroethane and nitroaromatic compounds are several decades. In this study, the optimal conditions to detoxify chlorinated compounds by the reductive degradation were investigated. The following results were obtained in the reductive degradation of CCl$_4$, C$_2$Cl$\_$6/, C$_2$HCl$\_$5/, C$_2$Cl$_4$, and C$_2$HCl$\_$5/ by using Fe, FeS and FeS$_2$ as mediators. CCl$_4$ was reduced to CH$_2$Cl$_3$ and CH$_2$Cl$_2$in anaerobic conditions when FeS was used as a mediator. While the reduction of CCl$_4$ to CHCl$_3$ was rapidly proceeded, the reduction of CHCl$_3$ to CH$_2$Cl$_2$ was occurred slowly. Further reduction to CH$_3$Cl was not observed. Unlike CCl$_4$, C$_2$Cl$\_$6/ was degraded to C$_2$HCl$\_$5/, C$_2$Cl$_4$. C$_2$HCl$_3$ and cis-1,2-C$_2$H$_2$Cl$_2$ by complicated pathways such as hydrogenolysis, dehalo-elimination and dehydrohalogenation. A small amount of C$_2$HCl$\_$5/ was detected only in the early stages of the reduction. However, majority of the C$_2$Cl$\_$6/ was reduced to C$_2$Cl$_4$. cis-1,2-C$_2$H$_2$C1$_2$ was the only product among other possible isomers.