The data from the EPA/Region I Summer 1975 Northeast Oxidant Transport Study have been collected, validated, and compiled by SRI. The final product is a comprehensive data base for the study, stored on a single reel of magnetic tape. The manual describes the content and format of this magnetic tape. Both air quality and meteorological data, from ground stations and aircraft, are included for the study, which began on July 15 and ended on August 31, 1975. Four aircraft covered different geographical areas throughout the Northeast. The aircraft were operated by Battelle Columbus Laboratories, Washington State University, the Interstate Sanitation Commission, and EPA (Las Vegas). Ground station data are included for Massachusetts, New York, New Jersey, Connecticut, and Rhode Island. Detailed hydrocarbon analysis for samples collected aloft and on the ground were conducted by Washington State University and EPA (Research Triangle Park) and are reported in the master file. Upper air data (rawinsondes, pibals, and the Albany ozonesonde are also reported for the study period.