INTRODUCTION The data analysis in this report has the objective of seeking quantitative relationships among the gaseous pollutants that react to form photochemical smog. These relationships will be used in future work to validate mathematical models that relate air quality to source and dispersion parameters. Combined with laboratory findings@ the results of the atmospheric data analyses aid in setting control requirements for achieving the greatest possible reduction in harmful effects on receptors. Measurements 1@2 made by Scott Research Laboratories in the Los Angeles area provide the input information employed in the analysis. The National Air Pollution Control Administration (NAPCA) and the Air Pollution Research Advisory Committee (APRAC) of the Coordinating Research Council (CRC) jointly sponsored the Los Angeles field programs in the fall of 1968 and the fall of 1969. Scott Research Laboratories monitored both air composition and meteorological quantities at two ground based stations each year. On some days they used aircraft to obtain additional samples. During the first year fixed stations were located at Huntington Park and El Monte@ These cities lie along a line which approximately parallels the prevailing wind direction late in the morning and in the afternoon during the fall months. The Commerce station replaced the one at Huntington Park during the second season of sampling. Fixed wing aircraft measurements were made both years@ but they were augmented with helicopter measurements during the second season. An Environmental Science Services Administration (ESSA) cooperative program supported the helicopter measurements to track air parcels by attempting to follow tetroons free balloon in free flight. Chemical analysis data from helicopter flights is reported in Ref. 2; however@ the tetroon trajectory data are only available to us through the kindness of Dr. Donald H. Pack@ Deputy Director of ESSA's Air Resources Laboratories. Evidently@ many months of processing will be required before their data become available in final form because ambiguities must be removed and averaging techniques must be applied. *A tetroon is a constant volume@ lighter-than-air vehicle which flies freely and is intended to follow mean air currents horizontally.