A field study of precursors to the formation of ozone was conducted in Atlanta during summer, 1990, in which average concentrations of C2 - C10 volatile organic compounds (VOCs) were measured hourly at six sites by an automated gas chromatographic system. If the source profiles of the prominent VOC sources are known, chemical mass balance (CMB) receptor modeling can be applied to obtain the contribution of each source to the measured ambient concentration of total non-methane organic compounds (NMOC) in each sampling period. Dispersion information can then be used in a subsequent step to obtain VOC source emission rate estimates, which are independent of emissions inventories derived by traditional methods. Results from the first step of the procedure are given, in which a subset of ambient data from the Georgia Tech site was analyzed by CMB to extract the motor vehicle exhaust contribution to ambient NMOC. Future implementation of the second step is also discussed.