Several research groups combined efforts to measure simultaneously the available ultraviolet radiation of the urban atmosphere of Los Angeles under representative environmental conditions. The study was planned to permit evaluation of possible methods of measuring the UV radiation important in photochemical reactions and to obtain preliminary data on the UV radiation energy with respect to location, elevation, and time of day. Measurements were made on five days at various levels of air pollution ranging from no smog to moderate-to-heavy smog. The report is a compilation of data obtained by the several participants, with brief accounts of instrumentation and procedures. The instrumental sensors used to detect the UV radiation were filter photocell, filter phototube, photochemical sensors, photosensitive plastic, and photochromic glass. Air quality and meteorological data for the sampling periods are also presented. A discussion and summary relates the data obtained in measurements by the different methods and at the various locations. (Author)