Cytochrome P450cam (CYP101A1) from the soil bacterium Pseudomonas putida oxidizes camphor regio- and stereoselectively at the 5-position, to give 5-exo-hydroxycamphor. Previously, we randomly mutated P450cam and selected seven mutants on the bicyclic polychlorinated insecticide and persistent organic pollutant, endosulfan (ES). Here we describe the activity of the seven mutants of P450cam with ES diol, ES, ES lactone, ES ether, ES sulfate, and heptachlor. ES diol, ES lactone, ES ether, and ES sulfate are persistent biotransformation products of ES in the environment. They all have the hexachlorinated norbornene (bicyclo[2.2.1] hept-2-ene) moiety intact. The P450cam mutants (and to a small extent the wild type) convert these substrates to substituted ortho-quinones, which we detected using 4-aminoantipyrine (4-AAP) in spectrophotometric assays. Here we have studied dehalogenation of ES and related compounds catalyzed by the endosulfan–selected P450cam mutants, using in vitro kinetics, chloride release assays, and 13C labeled endosulfan diol. We found that mutants ES7 (V247F/D297N/K314E) and ES6 (G120S) were significantly more active towards ES diol than the WT. On average, close to six Cl- ions are released per aromatic product detected upon turnover of ES diol. Finally, product isolation from reactions with non-labeled and 13C labeled ES diol confirmed that substituted catechols formed. Based on these findings, we propose that dehalogenagion begins with the oxidation of the ES double bond on the norbornene system, proceeds with eliminating six chloride ions and loss of the bridge as CO2 to furnish an ortho-quinone, which can be reduced non-enzymatically to the corresponding catechol.