The inter-annual variability of trace gases in the equatorial lower stratosphere is examined in order to explore the usefulness of comparisons between measurements from LIMS and UARS satellite instruments. The quasi biennial oscillation (QBO) is simulated in a two dimensional model by relaxing the modelled equatorial winds towards observed values. It is shown that during the LIMS data period the QBO was in the opposite phase to that expected during the first winter of the UARS measurements. The model predicts that LIMS measurements of ozone, NO2, and HNO3 may have been up to 30% less than the long-term average in the equatorial lower stratosphere while the first few months of UARS measurements may observe abundances up to 30% more than the long-term average. The importance of taking this variability into account and the desirability of several complete cycles of the QBO in the derivation of climatological values is noted. ¿ American Geophysical Union 1992 ¿ American Geophysical Union 1992