Reductive dechlorination of chlorinated ethenes has typically been modeled using standard Michaelis-Menten kinetic equations, implying that each dechlorination step is catalyzed by a unique biological factor. An alternative kinetic model is based on the assumption that all steps are mediated by a single factor. These two options are considered in the context of chlorinated ethene degradation by a previously characterized anaerobic culture. Competitive kinetics afford better chi-squared and visual fits of the data set tested.