This paper presents the first comparison of the zonally-averaged global distribution of total ozone obtained simultaneously using measurements from the Nimbus IV BUV experiment (refined as of December 1977), the Nimbus IV IRIS experiment, and the ground-based Dobson and ozonometer instruments of the World Meteorological Organization. The measurements are compared with respect to differences between measured latitudinal and seasonal variations of total ozone, with emphasis on any systematic discrepancies that appear to be related to differences in the sensing methodologies or instruments. While the zonal averages of the two satellite techniques agree quite well at low latitudes, the results are consistently higher for IRIS than for the BUV above mid-latitudes in both the Northern and Southern Hemispheres. The differences grow larger with increasing latitude, becoming as great as 23 percent at 75 ¿N during July through October. In the Southern Hemisphere, 49 out of 50 IRIS zonal averages between 25 ¿S and the :i South Pole are greater than the BUV averages. These persistent differences may be evidence of disparities between the infrared and ultraviolet methodologies or instrumentation. The BUV and ground-based ultraviolet averages agree better in general with each other than with the infrared IRIS averages. Inclusion of ozonometer data is found to generally improve the agreement between the Northern Hemisphere ground-based and satellite zonal averages.