Radiolabeled tetrachloroethene (PCE) and carbon tetrachloride (CT) were added to batch systems containing a lactate-enrichment culture displaying apparent dehalorespiration abilities to analyze the influence of mixtures on product distribution. Both CT and PCE were readily dechlorinated, although significant carbon disulfide (CS2) formation was observed during CT transformation. Calculated 1,2-14C-PCE recoveries for biotic treatments were between 91 and 104%, but an inability to recover products such as CS2 led to lower recoveries of 14C-CT (55 to 62%). While the majority of activity in 14C-CT-spiked treatments was recovered in the volatile fraction, 14CO2 increased significantly over time. 1,2-14C-PCE was primarily recovered in volatile and non-strippable fractions, but a significant increase in 14CO2 relative to cell-free controls suggested that the presence of a non-specific dechlorination pathway complementing dehalorespiration. The addition of both CT and PCE inhibited the transformation of the individual compounds and reduced the percentages recovered as 14CO2. However, the magnitude of these reductions was not severe and appeared to be the result of slower overall transformation rather than a complete inhibition of mineralization pathways.