Experimental measurements of scalar quantities in laminar counter-flow diffusion flames of mixtures of trichloroethylene (TCE) with methane have been compared with an equilibrium calculation. The data are correlated in terms of a mixture fraction. Data for stable major and minor species were obtained by using gas sampling with gas chromatography (GC) and a GC/mass spectrometer in flames with high (248 s−1) and low (175 s−1) strain rates. Calculations indicated that TCE mass fractions at equilibrium were very small, even at a relatively low temperature (600 K). However, the GC measurements showed that TCE persisted well into the flame. Strain rate was found to have a small but measurable effect on the correlation of species mass fractions and temperature with mixture fraction. The comparison of equilibrium predictions with measurements in mixture fraction space suggests that finite rate chemistry and chemical kinetics should be considered in the modeling of chlorinated hydrocarbon turbulent diffusion flames. This conclusion also applies to products of incomplete combustion such as the chlorinated polyaromatic hydrocarbons. A laminar flamelet model for turbulent diffusion flames of chlorinated hydrocarbons should yield significantly better results than an equilibrium model of the thermochemistry.