Chlorinated and brominated compounds belong to the class of organohalogen compounds that have received attention because of their widespread occurrence, use and applications. Understanding the sources and transformation processes of these contaminants in the environment enables assessment of their possible impact on humans and ecosystems. Recently new and innovative methods of Compound Specific Isotope Analysis have started to be applied to characterize the origin and fate of compounds, their breakdown products and degradation rates in different environmental compartments. Almost all studies have focussed on determination of isotopes of C and H, only recently new methodologies have been developed to measure isotopes of Cl and Br. This review firstly gives a brief description of chemistry properties and geochemical cycle of chlorine and bromine followed by a summary of their uses and applications. In the second section, an overview of CSIA techniques and new challenges and successful applications are also presented.