A comprehensive survey of the atmosphere of the Los Angeles Basin was conducted during the period August 22 to November 14, 1968. A large number of contaminants were determined continuously and periodically, and readings of pertinent meteorological factors were made at two ground level sites and in an aircraft at several altitudes above the ground sites. Mobile trailer-type laboratories were used in this study. The trailers contain instrumentation for continuous monitoring of a number of contaminants, photochemical products and meteorological parameters. The pollutants measured included carbon monoxide, oxidant, ozone, nitric oxide, nitrogen dioxide, total hydrocarbons, individual C1 to C10 hydrocarbons, peroxyacetyl nitrate, formaldehyde, acrolein and total aliphatic aldehydes. The meteorological elements monitored included temperature, relative humidity, wind speed and direction, and ultraviolet radiation intensity. The most significant advance was the chromatographic determination of more than 100 individual hydrocarbons. (Author)