Three Fourier transform infrared (FTIR) spectrometers were on board the NASA DC-8 during the second Airborne Arctic Stratospheric Expedition (AASE II) in 1992. Two FTIRs used solar absorption and one used thermal emission. We compare over 2000 measurements from these 3 FTIRs, on 12 DC-8 flights, for closely coincident air masses and times both inside and outside the polar vortex. In the majority of cases the offset biases are quite small, in the range 1--4%, and comparable to the absolute precisions expected. In most cases the rms scatter is in the range 4--11%; this scatter is unlikely to be geophysical, but rather is probably instrumental or analytical in origin. ¿ American Geophysical Union 1994