We have measured seven far-infrared rotational lines of HF and HC1 from a balloon platform at 28.5 km. Other lines, including H2O and O3, were observed simultaneously. At an effective altitude of about 33 km, we find an abundance ratio HF/HC1 = 0.18¿0.02, and a water vapor mixing ratio of about 4 ppmv. Modelled vaalues of HF/HC1 for an atmosphere containing this much H2O are slightly higher, but in reasonable agreement.