Infrared solar observations made by balloon at 27.9 km altitude in April 1976, and from the ground station of the Jungfraujoch, Switzerland, in October 1976, have confirmed the presence of hydrofluoric acid in the upper stratosphere. An average value of (3.6¿.7) ¿10-10 ppv has been deduced for the concentration of HF above 27.9 km. The comparison between the ground- and the balloon observations tends to indicate that over 50% of the total atmospheric HF is located above 25 km altitude.