Chlordecone (C10Cl10O; CAS number 143-50-0) has been usedextensively as an organochlorine insecticide but is nowadays banned under TheStockholm Convention on Persistent Organic Pollutants (POPs). A search forchlordecone-respiring organisms and choosing between reductive versusoxidative remediation tools and strategies to clean up chlordecone-pollutedenvironments would bene!t from the availability of Gibbs free energy data ofchlordecone and its potential dechlorination products. Presently such data are not available. Polycyclic 'cage' molecules of which chlordecone is an example contain considerable strain energy. It is not a priory clear how this a"ects the thermodynamic properties of the chlorinated members of this unique class of compounds and to what extent redox potentials for the halogenated congeners are di"erent from those of other aliphatic and aromatic organohalogens. We performed ab initio quantum chemical calculations to estimate #fHm° and #fGm° values of chlordecone and selected dechlorination products and used these data to calculate their Gibbs free energy and redox potential. With redox potentials in the range of 336'413 mV chlordecone has an E°! value similar to that of other organochlorines. The results indicate that there are no thermodynamic reasons why chlordecone-respiring or -fermenting organisms should not exist.