A complete set of mathematically identifiable and meaningful kinetic parameters estimates is needed to accurately describe the activity of individual populations that dehalorespire tetrachloroethene (PCE) and other chlorinated ethenes. These data may be difficult to extract from the literature because kinetic parameter estimates obtained using mixed cultures may reflect the activity of multiple dehalorespiring populations, while those obtained at low initial substrate-to-biomass ratios (S-0/X-0) are influenced by culture history and are generally not relevant to other systems. This study focused on estimation of electron donor and acceptor unilization kinetic parameters for the heterotrophic dehalorespires Desulfuromonas michiganeensis strain BB1 and Desulfitobacterium sp. strain PCE1. Electron acceptor utilization kinetic parameters that are identifiable and independent of culture history, i.e., intrinsic, could be estimated at S-0/X-0 >= 10, with both concentrations expressed as chemical oxygen demand (COD). However, the parameter estimates did not accurately describe dechlorination kinetics at lower S-0/X-0 ratios. The maximum specific substrate utilization rates (q(max)) fand half-saturation constants (Ks) for PCE and trichloroethene (TCE) estimated for the two heterotrophic strains are higher than values reported for Dehalococoides strains that can metabolize a range of chlorinated ethenes may be to respire dicholoroethene and vinyl chloride produced by Desulfuromonas and Desulfitobacterium strains or other populations that dechlorinate PCE and TCE at faster rates. Few data exist on the electron donor utilization kinetics of heterotrophic dehalorespirers. The results of this study suggest that Desulfuromonas and Desulfitobacterium strains should be able to complete for organic electron donors with other heterotrophic populations in the subsurface. Biotechnol. Bioeng. 2009;104: 301-311. (C) 2009 Wiley Periodicals, Inc.