Error introduced by Mount Pinatubo aerosols in total ozone derived by the backscatter ultraviolet (BUV) technique is described. BUV instruments include the total ozone mapping spectrometer (TOMS) instrument flying on Nimbus 7 and Meteor 3 satellites and solar backscattered ultraviolet (SBUV 2) instruments on NOAA weather satellites. Radiative transfer calculations show that except at very high solar zenith angles, errors in total ozone derived from the aerosol-contaminated radiances are less than 2% and vary both in magnitude and in sign with angles of observations. At solar zenith angles greater than 75¿, total ozone values may be underestimated by as much as 10% if a large concentration of aerosols is present near the ozone density peak. In subsolar latitudes, error in total ozone derived from TOMS as a function of scan angle is very sensitive to the aerosol size distribution parameters. Aerosol parameters derived from these data agree well with in situ measurements. ¿ American Geophysical Union 1993