We present an analysis of correlations between O3, NOx reaction products (NOz), and peroxides in photochemical models for polluted environments in comparison with measurements in the vicinity of Nashville, Tennessee. This analysis is associated with the use of O3/NOz, H2O2/NOz, and similar ratios as indicators for the relative impact of NOx and hydrocarbons (volatile organic compounds, VOC) on ozone formation. The measurements are used both to evaluate the NOx-VOC indicator theory and to identify NOx-VOC chemistry in Nashville. Results show that a linear correlation exists between O3 and the sum 2H2O2+NOz, consistent between models and measurements. The ratio O3/2H2O2+NOz has a near-constant value in both the Nashville urban plume and surrounding rural area. A similar correlation is found with total peroxides (O3 versus 2peroxides+NOz) but with greater scatter. The correlations between O3, NOz, and peroxides are consistent with an assumed dry deposition rate of 5 cm s-1 for H2O2 and HNO3. Changes in dry deposition and RO2 reaction rates cause minor adjustments in the NOx-VOC-indicator analysis for H2O2/NOz. Measured indicator ratios for Nashville are close to the NOx-VOC transition predicted by models and form an intermediate point between previous measurements for Atlanta (NOx sensitive) and Los Angeles (VOC sensitive). The model ozone production efficiency (P(O3)/L(NOx)) is 3--4, significantly lower than would be derived from the O3-NOz slope (5--8). ¿ 1998 American Geophysical Union