Near infrared absorption spectra covering the 1-0 bands of HF and HCl were recorded with a high resolution Michelson interferometer during a balloon flight near Broken Hill, Australia (30.5 ¿S, 138.5 ¿E) in March 1977. The ratio of the number density of HF to that of HCl as a function of altitude in the stratosphere was deduced from measurements of the R1 features of both gases. The experimental errors vary over the altitude range covered by the measurements, their estimated values being ¿25% between 14 and 30 km, increasing to ¿50% at the extremes of the range (14 and 38 km). Within these estimated errors the ratio is constant, its mean value being HF:HCl=0.1. ¿ 1977 American Geophysical Union