A methodology for mapping the spatial distribution of air pollutants by computer is presented. Using input data from discretely located air monitoring stations, estimates of pollutant concentrations are computed at 1.2-mile (2-km) increments between stations by two-dimensional interpolation. Maps are then printed to show the resulting distribution. Oxidant data are displayed in both measured units (e.g., pphm) and as Pollutant Standards Index values. Practical applications examined include the use of mapping to site air monitoring stations, providing public information, preparation of environmental impact studies, and conducting trend analyses.