The objective of this program is to measure species concentrations and their statistical properties at points in well-characterized chemically reacting turbulent flows. Such measurements are required for (i) testing theories of reacting turbulent systems and (ii) as input to models which predict the behavior of practical combustors. The model chemical reaction being used to study turbulent mixing/reacting flows is the NO/O3 reaction. A photolysis/chemiluminescence technique is used to measure reactant concentrations, (NO) and (O3), and a product concentration, (NO2), simultaneously at points in the flow field. From such measurements, the required statistical quantities, i.e., probability density functions (pdf) and correlations of reactants and product concentrations, are being developed. These data are supplemented by measurements of the turbulence power spectra and intensity at the same points. During this quarter an examination of the signal collection optics has led to readjustments with reduced errors.