Recent laboratory and field results demonstrate that different chlorinated aliphatic hydrocarbons (CAHs) ultimately can be transformed into innocuous chemical compounds in many aquifer systems. Transportation can be the result of either cometabolic reactions or reduction oxidation (redox) reactions. Several methodologies may be used to estimate the rate of reductive dechlorination of CAH compounds when they are being used to oxidize BTEX compounds. Both first-order and second-order approximations of CAH degradation rates can be useful in predicting CAH/BTEX plume behavior, although the second-order approximation will be especially useful in determining whether the system will first exhaust the available supply of electron donors (i.e., starve) or electron acceptors (i.e., strangle).