The long-term data collection of total ozone estimates from the Solar Backscatter Ultraviolet Ozone Sensors (SBUV and SBUV/2) began with the launch of SBUV on NASA's Nimbus-7 spacecraft in 1978. Following this successful demonstration, the National Oceanic and Atmospheric Administration (NOAA) adopted the slightly modified SBUV/2 instruments for placement on the afternoon Polar-Orbiting Operational Environmental Satellites (POES). The SBUV/2 instruments have flown on NOAA-9, -11, -14, and -16 in the POES series, with NOAA-16 launched in late 2000. Three more instruments are scheduled for launches in the next 6 years. While the absolute calibrations of individual instruments are good, they give total ozone accuracies of approximately 2%. However, without further adjustment, such interinstrument differences pose significant problems for atmospheric ozone trend analysis. In this paper we use the differences between total ozone estimates from the instruments during periods with overlapping coverage to account for these possible calibration biases. We use the NOAA-9 SBUV/2 record as the reference standard because of the length of its record and the amount of overlap with other instruments' records. By applying adjustments to the other data sets based on these differences, a complete, unified data set is created for use in analysis of long-term changes. The monthly-averaged total ozone time series for 50¿S to 50¿N and the hemispheric subsets are compared to the results from two 2-D chemistry models as a demonstration of the usefulness of the unified data sets.