We quantify the tropospheric ozone budget over remote high northern latitudes in summer using chemical and meteorological measurements between 0 and 6-km made during the summer 1990 Arctic Boundary Layer Expedition (ABLE-3B). We include all components of the ozone budget, both sinks (in situ photochemical loss and deposition); and sources (in situ photochemical production, advection of pollution ozone into the region, production in biomass wildfire plumes, and downwards transport from the upper troposphere/stratosphere). In situ production and loss of ozone are calculated with a photochemical model. The net influx of pollution ozone from North America and Eurasia is estimated from the average enhancement ratio of DO₃/DC₂Cl₄ observed in pollution plumes and scaled by the net influx of C₂Cl₄. The contribution of ozone produced in biomass wildfire plumes is estimated from the average enhancement ration of DO₃/DCO in aged fire plumes. Regional photochemical production and loss in the 0-6 km column are found to be approximately equal; hence, net photochemical production is near zero. However, when ozone production and loss terms are separated, we find that dispersed in situ photochemical production driven by background NO_x levels (5-10 pptv) is the largest source term in the ozone budget (62%). Influx of stratospheric ozone is of secondary importance (27%), long-range transport of pollution ozone makes a small contribution (9%), and photochemical production of ozone within biomass wildfire plumes is a relatively negligible term (2%) in the budget. Biomass fires and transport of anthropogenic pollution in the region may however have a major effect on the ozone budget through enhancement of background NO_x mixing ratios which increase dispersed photochemical production. Using a 1-D time-dependent photochemical model between 0 and 6 km, we obtain good agreement between the observed and model-generated vertical ozone profiles. We find that in situ photochemistry within the 0-6 km column accounts for nearly 90% of the ozone mixing ratio within the boundary layer, while above 5 km it accounts for only about 40%. Although photochemical production of ozone within the 0-6 km column is larger than the other source terms combined, the 1-D model results indicate that influx from above is necessary to account for the observed increase in ozone mixing ratios with altitude.