This report presents comprehensive summaries of data produced by the nation's ambient air quality monitoring activities for 1975. The data are summarized in two formats: frequency distribution (Part I) and status of data with reference to standards (Part II). These summaries are based on data acquired through extensive monitoring activities conducted by Federal, state, and local pollution control agencies and submitted to the U.S. Environmental Protection Agency's National Aerometric Data Bank. Information is provided on the six pollutants for which National Ambient Air Quality Standards have been set: total suspended particulates, carbon monoxide, sulfur dioxide, nitrogen dioxide, total hydrocarbons, and total oxidants. Part II does not include a section for hydrocarbon data since the hydrocarbon standard was established as a guide for meeting the oxidant standard and monitoring for hydrocarbons is not currently required.