Chlorinated ethylenes, (CE), specifically perchloroethylene (PCE) and trichloroethylene (TCE), are widespread groundwater pollutants listed EPA priority pollutants. The catalytic dechlorination of CE by 5,10,15,20-tetrakis-(4-carboxyphenyl)-porphyrin cobalt ((TCPP)Co), a cobalt complex structurally similar to Vitamin B12 was studied. It has superior aqueous phase dechlorination activity against CE relative to Vitamin B12. Through kinetic analysis, the rate laws for PCE and TCE were determined to be first-order in substrate and catalyst, and PCE degradation was sensitive to the concentration of the titanium citrate bulk reductant and pH. The importance of the CoI oxidation state on dehalogenation was studied. This is an abstract of a paper presented at the 230th ACS National Meeting (Washington, DC 8/28/2005-9/1/2005).