Using a spatially weighted average of SAGE 1 measurements, we find 337 colocated SAGE 1 and Umkehr ozone profiles. The total column ozone above 250 mbar measured by SAGE 1 averages 5% higher than that measured by Umkehr. This difference is concentrated in the lower stratosphere and, for latitudes poleward of 30¿ N, the difference depends on both the total column ozone and the season. The difference, however, is insensitive to the stratospheric aerosol optical depth measured by SAGE 1. Intercomparison of SAGE 1, SBUV, and Umkehr ozone at stations north of 30¿ indicates that in layer six (approximately 10 mbar) Umkehr values are approximately 10% high, and in layer eight (approximately 3 mbar) SBUV ozone is approximately 10% high. In the upper stratosphere, the SAGE1-Umkehr ozone differences are small for low stratospheric aerosol optical depth cases (less than 0.025 at 0.3 μm) but vary from -3% in layer six to -8% in layer nine for high optical depth cases (greater than 0.025). This tendency is opposite to that predicted by empirical studies, which included large amounts of volcanic aerosols, and by theoretical model studies. ¿ American Geophysical Union 1987