We compare volume mixing ratio profiles of N2O, CFC-11, CFC-12, CCl4, SF6, and HCl in the mid-latitude lower stratosphere measured by the ATMOS Fourier transform spectrometer on the ATLAS-3 Space Shuttle Mission with in situ measurements acquired from the NASA ER-2 aircraft during Nov 1994. Good agreement is found between ATMOS and in situ correlations of [CFC-11>, [CFC-12>, and [SF6> with [N2O>. ATMOS measurements of [CCl4> are 15% high compared to ER-2 data, but agree within the systematic uncertainties. ATMOS observations of [HCl> vs [N2O> are within ~10% of ER-2 data for [HCl>>1 ppbv, but exceed in situ measurements by larger fractional amounts for smaller [HCl>. ATMOS measurements of [ClONO2> agree well with values inferred from in situ observations of [ClO>, [NO>, and [O3>. The sum of [HCl> and [ClONO2> observed by ATMOS, supplemented by a minor contribution from [ClO> estimated with a photochemical model, is consistent with the levels of inorganic chlorine inferred from in situ measurements of chlorine source gases. ¿ American Geophysical Union 1996